Chris Smolinski wrote:
>
> If there's anyone who's played with magnetometers and can offer
> some advice (or maybe recommend another inexpensive commercial
> unit, or a  build-it-yourself option) I'd appreciate it.
>

Honeywell has a lowcost magnetic field sensor that was used
by one of the app's people at Byte Craft when he put
together a low cost compass. As I recall it was easy to work with,
he had that part of the project running in about a day.

Walter Banks
http://www.bytecraft.com