Tyler and Andrew talked magnetometers, and how we can get an attitude reference if we use a model of the Earth's Magnetic Field. Can we extract a 1D polynomial approximation to the global 3D model? Or do we need the whole thing? Can we get the source to the World Magnetic Model (WMM)?
We're still waiting to hear back from Honeywell as to which sensors they're willing to sample us.
Update (March 24 2004): we've gotten the sensors from Honeywell, see the MagnetometerLv2 page for details.