I think I would be looking for an electro-mechanical solution to this problem rather than an electronic one, perhaps two long lever micro switches fitted back to back or something...but as long as you're in the mood for an electronice one, can you not just detect the lever change over action with a couple of photo detectors ? If you can, then it's a simple matter of constructing a change over with a relay instead of the switch...
Current draw is perhaps one way of detecting when it's stalling, however anything that causes it to draw more current will upset your circuit.