We've covered Cellbots
on Android Community before, an open-source way to use your smartphone as a brain for a simple robot, but the project has released a new java app
which supports not only custom, Arduino-based Cellbots but iRobot Create, LEGO MINDSTORMS and VEX Pro. Requiring Android 2.2 or above, the new app allows you to either remotely control the robot using the phone as a navigation pad, or alternatively mount the phone directly onto the robot and use it as the 'bot's brain.
There's support for spoken commands, streaming video and even using a second Android phone running the app to work as a remote (while the first is in brain mode). It's a free download from the Android Market.