I've worked on AppMobi, iOS(mostly), Android, Blackberry, phoneGap/appMobi and J2ME development and they always keep me on my toes (because of the ever changing landscape).
I worked on the iOS and Android development of a contacts backup app called AirBook (Links to paid iOS, free iOS and free Android apps) that also lets you view your address book on somebody else's phone (iOS or Android) in case of an emergency!
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