The previously web-only Boomerang app for Gmail is now in open beta on Android. Just another mail app, right? Not quite -- Boomerang's hook is that it can bring unanswered messages back to your inbox. More than a clever reminder system, the app uses gesture controls (swipe right to archive, left for snooze and other options) and can schedule outgoing emails, too. According to TechCrunch, developer Baydin is also working on support for non-Gmail services and a tablet-optimized app. Jump to the Google Play link below to get your hands dirty for free.