The T-Mobile G1 is the commercially available version of Google's first foray into the world of mobile phones. The hardware is by HTC Corporation. To Amarok (1.4.10 at this update), the device is configured as a Generic Audio Player. For instructions, see iRiver X20.
This section of the Amarok Wiki will be updated soon with info on a better plugin for this device. I'm just starting on it today (10 Mar 2009), but planned features include transcoding media for space savings (phone ships with a 1GB microSD card), adding album art The Amarok Way (phone already reads art if it's part of the ID3 tags - but that's a heck of a waste of space), etc. Let me know if you want more.