Garrett is a playground for Duby exploration on Android.
Garrett is named after Garrett P. Serviss, the hero of Edison's Conquest of Mars, a ridiculous late 19th-century space opera novel by Garrett P. Serviss.
Copy local.properties.example to local.properties and edit it to point to your SDK. If you're not targeting Android 2.1, you might need to edit default.properties too.
You'll need Duby checked out, compiled, and on your path. At the time of this writing, the "super_fixes" branch must be used.
Then you should be set to do "ant debug", and an .apk file should be generated in the bin/ directory. You should then be able to install it using "adb install" or by putting it on a public web server and navigating to that URL from your device.