iOS: If you have friends who speak a language you don't, communicating over text message is almost impossible. Slated is an iOS keyboard that translates while you type, and can also translate what's sent back to you.
When you have Slated loaded up as keyboard in iOS 8, you just need to type whatever you want, then tap the "..." button to pick a language to translate it to. It's incredibly simple and useful when you're trying to talk with someone who speaks a language you don't. The accuracy isn't perfect, but it gets the job done.
Slated ($6.49) [iTunes App Store]