I've thought about this myself on a larger scale...to stop it from travelling too far either wire up some microswitches near the axe shaft so it turns off the relay or speed controller at each end of its swing, or just let go of the Tx switch when it's gone far enough :P

ESC would depend on what motor you end up using, you can just use relays (one for forward, one for back) but if you go for an esc get one rated in excess of the stall current of the motor, because it will approach that current if it hits something and gets stuck in the armour.