Good Gear Guide
In pictures: 15 must-have iOS apps you can't get o...
IFTTT (iPhone, iPad and iPod touch)
IFTTT stands for "If This, Then That." That's the basic premise behind the app. You choose one smartphone function and set it to trigger another. For example, if you want to post all of your Foursquare checkins to Facebook, you'd create a recipe for "If This (Foursquare) Then That (Facebook)." The app offers a ton of user recipes that you can take advantage of, and the possibilities are endless. (Read more specifics about IFTTT here.)
In pictures: 15 must-have iOS apps you can't get on any other platform