I built a mediocre prototype around November, and am currently working on a hopefully better prototype.<p>Useful info about the following: I am a cheapskate, and am interested in producing this very cheaply. If you're willing to drop $80 on the compass module, certain aspects of this will change.<p>My first prototype was built out of cell phone vibrating motors, a belt I stole from a friend that had good holes for the motors, and a compass from <a href="http://www.robsonco.com/Dinsmore/" rel="nofollow">http://www.robsonco.com/Dinsmore/</a>. It worked alright, but the motors were prone to getting stuck, the compass module wasn't as consistent as I'd like (eg, it gave around 30 degrees to cardinal directions and 60 degrees to diagonals). To build this, you'd probably want basic soldering skills and preferably a basic understanding of electronics. If you were seriously interested I could send you instructions.<p>For my second prototype I'm using coin-type pager motors, so I don't need to worry about the heads hitting anything. Specifically, I'm using: <a href="http://www.pagermotors.com/index_files/Products/DiskL/DiskL.htm" rel="nofollow">http://www.pagermotors.com/index_files/Products/DiskL/DiskL....</a> (and fwiw I measured them at 40mA). I'm also using an AK8973 compass chip, although I haven't yet tested it. This is _not_ a hobbyist friendly chip, and it's kind of a pain to get. On the other hand, I got them for $7 a piece and I expect it to give me better accuracy than the Dinsmore module. I expect to use a microcontroller interpret the output and activate the motors (I may need more cir. For the belt I'm essentially using a canvas strap. To do all of this (mostly to deal with the newer compass chip) I've so far needed to etch my own circuit boards (you can get around this pretty easily for approx $20), will need to solder better than Santa's elves, and will need to program a microcontroller.