iOS: If you have a friend (or a few of them) who always seems to have a dead battery, Battery Share is an app where you can easily share your battery level with a select group of friends. In order for Battery Share to be useful, you and all your friends will need the app. From there, it works like a social network for you battery. Anyone you approve as a friend can see your battery percentage and they can see yours. If you want, you can set it up so you'll get alerts when someone's battery gets low. There's a built-in VoIP tool too, but that's not particularly necessary for most of us. Still, Battery Share's pretty clever and useful, albeit a bit niche for most of us.