A possible sensor for the toe / balance is a strain gage. It's a solid state device and can be located in any of several locations. Mounting it on the end of the toe might make it easy to access but leave it vulnerable to moisture and grime. I'm in favor of locating it at the other end of the actuator, near the ankle. Preassure would be read the same at either end. This sketch shows cylinder actuators but they might be worm gears or other linear electrical actuation.