Lisa Bernier

You're on vacation. You come across a landmark: the Eiffel Tower, the Empire State Building, the Pyramids of Giza—or the world's largest rubber-band ball. You wonder, how tall is it really? But you didn't get the audio guide. Well, whip out your phone and use the Smart Measure app, and the knowledge will be yours in just a few seconds.

If you are Neil Patrick Harris, you don't care who unfollows you on Twitter. If you are a normal person, though, you probably do want to know what jerk gave you a Twitter-ized "it's not you, it's me." Clearly you need the app JustUnfollow to stalk all those tweeps who reject you.