I've managed to get the HT to interface with my RC tx, and built a pan-tilt platform to test it. :
I've put the thing on my RC car and driven it around a bit. Works quite well. I've added a digital high-pass filter to the gyro input, so drift is reduced a bit, but it's still there.
I'm getting some weird RF interference problem though. When the TX antenna is extended, the gyro starts to get a bias. The good thing is the bias is constant, so the high-pass filter removes it after ~20s. I'm using a lightly shielded audio cable to connect the HT to Tx, maybe I'll try a better cable...