That's the second best use for a trolling motor IMO. I had to look carefully to see how the wheel is being driven. Looks like the prop has been replaced with a rubber roller and the friction drives the sidewall. Correct? I wonder how long the battery will last? I have a an old 3hp trolling motor in my attic....its got me thinking.
The 12v marine battery weighs at least 30lbs. I wouldn't want to strap that on to the back of my bike. What would a 12v lighter weight, state of the art equivalent battery cost? I would think in that configuration, you would need a freewheel, as to not be spinning the motor when pedaling.
-Mike