I wish to have a touchsensor on the end of a moving arm. However, through the Python API, getDevice('touch_sensor') only returns sensors that are directly under the Robot parent. 
Is there a way I can either get a sensor that is nested (under a joint), or instead make a sensor that is under parent move in tandem with another joint?
I have tried setting the bounding box of the sensor to a shape/transform nested under the moving joint, but it simply takes on the original position of the shape and doesn't update when the joint moves.
I have also tried putting the sensor directly under the joint, in which case it does indeed move, but then I cannot access it from the python API. (Using get device returns None)
Found the problem, I should have used getTouchSensor instead of getDevice!!
Now it works fine.
How to get TouchSensor nested under joint in Webots (Python API)