Hi, I lurk here a lot, don't fly RC, but like to hear about what you guys are doing. Here's an EDN "design idea" for an inertial navigation system. I have no idea how well it compares to similar-cost alternatives (if they exist). It uses a 3-axis accelerometer, three single-axis angular rate sensors, their amps, and a NEC uP.
formatting link
The CXL04M3 3-axis accelerometer has been replaced by the CXL04LP3 -- $349 at
formatting link