Hmm…now that I think about it, I think there’s an even easier mechanism that does the same thing.
Make an elevator that’s the width of the robot with two hooks, one on each side. If the bar is level, both hooks touch at the same time and the robot lifts straight. If the bar is tilted (let’s say your on the left side and the bar is higher on your end) then the left hook will touch first and carry all the weight of the robot. Once the robot gets off the ground, it will swing to the left so that its CoM is under the left hook. That moves the force further away from the pivot, which increases the torque on the switch. The same things happens in reverse if you’re climbing on the lower side: the right hook holds the weight of the robot and the CoM swings under it to the right, moving the force closer to the center and decreasing the torque on the switch.