Here’s a great project by John Brost. Inspired by Steve H. ‘Green Monster’ he built this model, which also uses Bluetooth GPS (and RobotC) to navigate around.
Voyager uses a 3-motor articulated steering design - one motor drives both wheels on the rear axle through a differential and the front wheels are driven individually by the other two motors. It also has a compass sensor and a GPS connected via bluetooth.

More pictures are found in NXTLog project page. Good work, John!

btw. Technically it IS possible to build a BT GPS NXT-G block. There’s a lot of work involved, and very little potential users. If anyone is interested, email me. I’ve posted a few posts on GPS in NXTasy, and since some implementations do work in NXC (under standard firmware) they can be ported and wrapped into a NXT-G block (but with a lot of effort).

Guy Ziv