Next time you're playing a favorite game on your iPhone and iPad, a huge ad -- or worse, a minute-long video roll -- might take over the screen. iAd platform's full-screen interstitial banner and pre-roll video ads, which were first announced earlier this year, are now available to developers. The full-screen ads appear as transitional screens, say, whenever you reach the end of a game level, while the video ads come in 15, 30 and 60-second variants. These are already available on other ad platforms, of course, but iAds were typically more unobtrusive, just banners that you can click on to launch advertisers' websites. As you'd expect, these new options will cost devs a lot more money. But if Apple does unleash an iPhone with a much larger screen (possibly this September), then these ads might just be worth their cash.