Servos move based on input frequency. That comes from a duty cycle of a given length. Each servo has a specific duty cycle that maps to a particular degree. For example, providing 1.5ms duty cycle @ 50hz to a standard hobby servo will move the shaft to the center position. Shorten the duty cycle to 1.0ms and the shaft turns all the way to the right. Lengthen it and it turns all the way to the left.

Are old friend the 555 can help us out here. Just building a servo tester would be useful. But you could do something like using a rotary switch to physically toggle a light switch. Isn't there a crowdfunding thing for just that?