Take a look at this one. It does not require a new wheel, and could probably be fitted to a unicycle.
Interesting but I bet it would be a pig to ride as a unicycle. Maybe they could change the software.
The problem I see here is, you’re still using a regular fixed/direct-drive unicycle wheel. This means when your wheel starts spinning faster than you can keep up with your pedalling, you’re going to go flying 
I think for an E-Uni to work, you need the drive to come somewhere between your pedals and the wheel - either that or you need to become a god at coasting!
I watched it again and you may be right. If the push kicks in suddenly with full force after half a second, it will be a uni rodeo. What I really want to do is mount this on my kids bikes. I have been wondering a long time about how I can get them up to 25 km/h.