[jurjenhaitsma]

I read about this a while ago (slashdot?) and thought it was quite intriguing myself. I believe there were some complications with withdrawal symptoms so buyer beware.

As for your request, most competent electronics hobbyists / engineers could likely build a crude version, but I could see complications arising from the vast number of electrical sources potentially disrupting your "north" signal.

Which led me to ponder a refinement - by using gps, although encoding location is quite a complication, it would be an incredible extension of the idea. A possible implementation would have latitude and longitude pads that could either vibrate at a varying frequency or (for extra leet points) activating a series of binary pads to encode the lat/long.