I am temporarily setting aside the webcam stuff because I had some handy motors dropped into my lap in the form of a pair of dead electric scooters. These run on 2 12v batteries in series for a 24v system. The design of these is fairly simple with only a few subsystems.
I spent a couple hours going through scooter # 1 to discover the switch was bad (these had been left out in the rain at some point) while learning the ins / outs of the system. Surprisingly the controller is composed of only one mosfet and a bit of glue logic to do PWM speed control and breaking. 24v at 10A drive is pretty impressive.
The speed control is done by way of a hall effect sensor with two magnets in the rotary controller. This results in a 1v - 4v control range. This could be mapped to a 5K potentiometer acting as a voltage divider of 5v. But below 1v and above 4 it wouldn't make any difference.
The break lever controls a drum break and activates a simple normally open switch. When this is closed the controller shuts down the motor.
For my testing purposes I will be pulling the motors / batteries out of the scooters and mounting them to my mobile device chassis. One each side. With some creative caster use I will then have a "Tank" drive system. The controllers are probably going to be replaced by standard reversible H-Bridge controllers.