OneBusAway has an official Android client. The app formerly known as SeattleBusBot is a native Android client for OneBusAway. You can find the app by searching for "OneBusAway" in the Android Marketplace.
SeattleBusBot was written by local Seattle developer. The app combines a lot of the same features found in the OneBusAway native iPhone app, but has some new bells and whistles too, such as bus arrival alarms and route bookmarking. And just like OneBusAway, .