I set aside a day with Sam Amin to do a teardown (my first!).
The cars each had a controller that turns left/right and drives forward/reverse, so at the least inside was a four channel receiver with a decent toy motor and some sort of turning mechanism- for only 6 bucks!
After four Phillips screws, the cover slides off.
The antenna still conncets the two though, so it also has to be unscrewed
What's really nice about this circuit is the clearly labeled board. The pins read Vcc, GND, M1-1, M1-2 (For the drive motor's +/-), M2-1, and M2-2 (For the turning motor's +/-). This should work nicely for any circuit you want to control remotely. The cars work on 27 MHz and 49 MHz, and like I mentioned before, the controller can do forward/reverse and left/right, so, with some diodes, you could control 4 on/off devices.