As a sign that the United and Continental Airlines merger is progressing well, United (which got to retain its name in the process) has launched an Android app that supports both United and Continental.
In fact, the app is so close to the existing Continental app that I'm pretty sure they simply ripped it apart and put back together after adding support for United into the mix, even leaving the logo the same. However, since the Continental app only supports Continental and the United one supports both, there's no reason to keep the former one installed anymore.
The United Airlines app supports flight check-in, storing of mobile boarding passes, booking flights, flight status (including push notifications - nice!), MileagePlus and OnePass account info, and other features.