I’ve been a daily wheelchair user for several years now, and my main wheelchair has an optional Smoov power assist attachment fitted. I attach the unit when I know I have upcoming expectations that I may need it.
It works by pushing the chair from behind and leaves steering, braking, and stopping the unit to the user. The associated phone app allows you to tune its performance, check its batteries and check diagnostics.
Mine has had one return issue which I feel would have been quickly resolved had the vendor immediately returned it to the Australian partner, rather than attempting to fix it themselves.
Apart from that it’s been an excellent unit, although using it safely is certainly a learned skill. For example while it can tackle fairly steep slopes, realise that if you stop it (traffic etc) there is scant chance you’ll be able to spare a hand off the brakes to start it going again.
Also if like me you’ve tuned it to push fairly forcefully, realise that you applying full brakes (holding the two main wheels stationary) may not be enough to stop it skidding you forward anyway.