As iOS developers, we have some hard choices to make when we consider which devices to focus on as we develop our apps. Though many of you will shrug this off and point to universal builds as the key to the big time, that’s a far too obvious approach, and you’re probably shaving off huge chunks of the user experience by creating a one-size-fits-all app. One size may fit all, but it’s rarely a good fit.

One of the most striking differences between iPad and iPhone is the screen estate, and the implications for interface-conscious developers – which we all should strive to be – are tremendous. While the screen area for iPhone/iPod touch measures 10.4 inches (4.54” x 2.3”), the iPad screen enjoys a full 71 inches of area (9.56” x 7.47”) – almost 8 times bigger! Think of it like building a home: with just a small plot of land you’ll focus on the essentials: bedrooms, kitchen, living room, bath… certainly no spare room. But given a bigger plot you‘ll want to add a garden, a couple of parking spaces, and for sure build in that spare room. The same principle applies to iPad vs iPhone in terms of the user experience on offer with these very different screen sizes.

On iPhone, the smaller screen area dictates a pretty minimal interface for your app, whereas on iPad there are amazing opportunities with the more generous area. That being said, for certain apps the same interface on either display may be comfortable for users, especially apps built primarily for media or information consumption. For example, an app like Night Stand shares almost the same user interface on iPhone and iPad, and has been a spectacular hit on both. Why? Well, for starters it’s gorgeous. And ingenious programming doesn’t hurt, either.  But also, once a user configures Night Stand it’s essentially an information consumption application (though the latest version brings in some more user-intensive features). Also, there’s one big exception with Night Stand for iPad, and that’s a new, iPad-only theme – one significantly awesome theme that really, REALLY shines on the big screen. But awesome themes notwithstanding, Night Stand still very much follows an app-to-user orientation; the user is still passive.

Nixie - beaming new gfx with subtle animations - only for iPad

The LCD color selection interface on iPad: a popover for live previews, on iPhone: small screen -> no popovers -> trip to the settings panel

On the other hand, consider some dual platform user-ACTIVE applications with upscaled interfaces for iPad. In the images here, iPhone is overlaid on top of iPad.  (Click to enlarge.)

Sketchbook Pro

Bento

Flight Control, with richer maps and gameplay

Dropbox, with file browser and media previews

So while Apple will most likely put iPhone and iPad on the same track of iOS in the very near future, developers ought not assume that these devices are the same in terms of UX, or that users have the same expectations toward iPad and iPhone apps. Nope, expectations are growing increasingly different as each day passes, and the gap is only widening.

Just a few days ago we were watching Toy Story on the iPad, and it was a cinematic experience in miniature with the lights dimmed and munching on some snacks. Two people huddled around an iPhone watching a film for 90 minutes!? Not unthinkable, but certainly none too appealing. No doubt, iPhone is much better suited to snagging a glimpse at Facebook, tapping out the odd Tweet, light email, checking your schedule, that kind of stuff. I tend to use my iPhone in bursts, to get or give info as quickly as possible without going into details, whereas iPad can offer an immersive media consumption experience, like watching a full length film in style. When I browse the App Store for iPad games and applications, I look for things I can be time-intensive with. (And I’m not alone.) When I shop for an iPhone app it’s usually for a cool little game, or the latest social networking app to stay connected with my people. And yeah, isn’t that what a phone is made for in the first place: to keep in touch with friends and family? Now if I can do that, plus spend 30 – 40 mins playing puzzles or doodling or something, well, all the better!

Note the Productivity category, with iPad sales far outweighing iPhone. Business, finance, education, and anything reading-related are also natural fits for iPad.

So developers, before you start building your next app take some time to decide whether it best suits iPhone or iPad – or both. And if both, then how to differentiate. iPhone/iPod touch has a user base of almost 100 million compared to just over 3 million for iPad, but there are over 200 thousand apps for iPhone and just a few thousand for iPad. Getting noticed in the sea of iPhone apps is not so easy, but if you optimize your universal app for iPad (or develop exclusively for iPad) along the lines of what we’ve been discussing it’s far easier to make a splash.

While all this was going on, of course there was some big news on June 7, when Steve Jobs introduced yet another Apple engineering marvel: iPhone 4.  Bundled with new features like front-facing camera, superior rear camera, dual mikes for increased noise cancellation, eye-popping Retina Display, multitasking, 720p HD video recording and even a new kind of gyroscope technology, iPhone 4 is a huge evolutionary step in smartphone design.  As the tag line says: “This changes everything.  Again.”  And, marketing hyperbole aside, as far as day-to-day use is concerned for sure this will change the way we use iPhone.

Before this year’s launch, several leaked – or mislaid – iPhone 4 models made the rounds of the major tech blogs, complete with gory dissections and the standard tsunami of specu-babble.  But there was one stealth feature all the teardowns and pundits failed to even guess at: the gyroscope.  And on our side, as veteran iPhone developers, when Steve Jobs announced this during WWDC we were all pretty excited.  And while it still hasn’t gotten much attention in the press, this feature is a game changer in iPhone’s rivalry with Android and Symbian devices.

Apple’s been pioneering smartphone innovations since iPhone’s introduction in 2007 with many widely imitated micro-technologies, in particular the accelerometer.  The accelerometer is a type of sensor that detects changes in a device’s orientation, vibration, rotation or fall by detecting linear acceleration along one of the three X, Y and Z axes – that is: up/down, right/left, and front/back.

3-axis accelerometers enable features we by now take for granted in smartphones (and lately, too, in non-Apple branded consumer digital cameras, music players, and gaming peripherals).  For example, landscape/portrait orientation shifting, tilt for directional control in games and applications, and shake features for refreshing a webpage or shuffling a playlist.  The 1st generation of accelerometer – pre iPhone 4 – could measure only linear motion; it couldn’t sense direction on a compass or twisting motions or rotation, nor had any notion of gravity.

Then last year Apple added a magnetometer to the iPhone 3Gs, enabling it to sense magnetized direction relative to the Earth’s poles. And now, with the introduction of the gyro in iPhone 4, Apple once more ups the ante in spatial detection / orientation with a new sensor for detecting 3-axis angular acceleration around the X,Y and Z axes, enabling far more precise virtualization of pitch, yaw and roll on iPhone.

While detection of change in velocity has been possible for some time thanks to conventional accelerometer calculations in terms of linear acceleration, the gyroscope has been designed to detect angular acceleration, which will detect change in both velocity and direction at the same time.  iPhone 4’s gyroscope enables the sensing of even slight degrees of rotation while simultaneously rejecting linear movements and hand jitters – both still ably handled by accelerometer’s linear movement detection technology.

Combining the 3 axes of the gyroscope along with the 3 axes of the accelerometer now enables iPhone to recognize distance, speed and direction as it moves real-time through space. And thanks to the CoreMotion APIs in iOS, developers with the vision to make use of gyroscope data can access it freely, as some have already done.

Of course iPhone 4 already includes gyroscope support, but it’s a safe bet the gyro will be baked into future versions of iPod touch, and naturally, iPad.  iPhone devs who can make use of this amazing new technology will find opportunities aplenty on the new platforms, especially games producers and developers.

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update:  Death Star or iPhone gyroscope?   iFixit has the goods.

True, iPhone 4 had been dissected, diagrammed and reported on ad nauseam even months before Jobs’ announcement, but that didn’t dampen our enthusiasm on release day. And despite the leaks coming out of Vietnam and hands-on time with stolen prototypes, what the prophets couldn’t prognosticate was how deliciously the hardware gooses the software.  Just consider iOS itself.  It’s a huge lift for developers, a massive gift from Apple for anyone with an eye to publishing for the App Store.

The first turn-on in iOS is multitasking, which depending on your application type can be achieved through one of 7 core background services Apple provides: background audio, voice over IP, background location, push notifications, local notifications, task completion and fast app switching.

The upshot of this is users will genuinely feel they’re multitasking, while the software is actually only running one app at a time, albeit with services.  So in terms of raw power that developers can exploit and direct toward their apps, we have the lion’s share of CPU, memory and other resources at our disposal.

Aside from multitasking, we also now have Game Center with integrated social networking, and this is going to change the gaming experience on iPod touch and iPhone forever.  And with the introduction of iAd, developers now have another revenue model with the potential for ad-supported apps distributed at no charge to users.  User reaction to in-app advertising has yet to be tested, but we’re already testing various configurations.

The introduction of app-specific location settings also means you don’t need to change your location each time you use a new application that requires setup with different locations.  The ability to gift apps is another nice feature with terrific upside for developers.

What else have we got to look forward to… ah yes, Spotlight now not only searches your device, but also the Web and Wikipedia.  In-page video playback for Safari is another lovely addition.  And iPhone 4 is now more enterprise-friendly with enhanced data protection, mobile device management, wireless app distribution and SSL VPN support. Wake on wireless, too, automatically re-connects you when your lost wireless connection is regained.  Places in photos offers other interesting possibilities and Mail has been completely revamped.

Spotlight with Web & Wiki search

Coming to the SDK, full map overlays means developers can implement a transparent map layer on top of screen contents, a boon for location-oriented utilities, games, and lifestyle apps.  And the AV Foundation framework for the first time gives developers full control over video playback and capture.  Full photo library and calendar access now gives developers the power to directly access these previously semi-restricted features.  Now, too, you can send short messages via your apps through in-app SMS, and Accelerate provides easy to use functions for your computational / number-crunching needs.  Another welcome addition are the Quick Look APIs, similar to OS X’s desktop version, giving users the ability to page through documents and other filetypes without needing to launch an app. The UIAutomation instrument, too, can be made to automate touch events, while Time Profiler and Energy Diagnostics Instruments can be used to fine tune your applications.

All these new SDK-side features represent a huge opportunity for iPhone developers to not just tack on new feature to existing apps, but to dream up entirely new creations and markets.  iOS and iPhone 4 mark another exciting chapter in Apple’s handheld lineup.  We can’t wait to show you what we’ve got in store.

PhoneGap is developed and designed by Brock Whitten, Rob Ellis, freelance designer Colin Toomey and Eric Oesterle.

[source PhoneGap]