Well, it's a bit ambitious for a second post, but I thought I'd get down to what got me here in the first place - an electric pusher for my Yaris - not to drive as an EV but to get it moving and beat enertia. What I'm thinking is that a very simple pusher could be made that would connect to a hidden hitch with square tube, come to a hinge, and an extension of square tube would extend from the hinge to a wheel (motorcycle, mountain bike, not sure yet). A spring in some configuration would hold the wheel down. The next part depends on the force needed to get the yaris moving - either a permanent magnet motor (perhaps a power steering motor), or a truck starter would directly drive the wheel. A battery will be kept in the trunk and completely separated from the car electrical system. If a permanent magnet motor is used, I hope it to regen the battery will the car is running. If a starter is used, I'll depend on it's solenoid to keep it from being turned while not engaged. I'm not sure about the recharging in that scenario. It might just require a deep cycle battery and a charger.
Problems up front:
Stir in the numbers - I'm going to have to determine what forces are involved and how fast the car is to get moving before shifting into gear and using gas.
The Yaris is under warranty - the whole works comes right off and leaves no trace excpt for the hitch. Problem is, Toyota "doesn't recommend" towing with the Yaris in the US. They even "don't recommend" using a hitch-mounted bike carrier. The exact same car in Canada can tow with Toyota's blessing, and they even sell a hitch for it.
So, I'd check with my dealership and see if they'll hold me not being able to use a hitch-mounted bike rack (or something).