please please try one before you commit...I have tried one in my professional capacity (retired occupational therapist) and wasn't very happy with it, it depends what your physical problems are.
>>>How do they get over needing electricity in the bathroom?
They don't. They use electricity in exactly the same sort of way that an electric shower does. i.e. everything is double-insulated and properly earthed, so there's no risk of an elecric shock. (There's also battery back-up, in case of a power cut).
Electricity in the bathroom is not a problem. You get electric showers, electric heaters, electric extractor fans and electric lights. They are all wired in and controlled by pull-cord switches. Socket outlets are not allowed, apart from shaver sockets with an isolating transformer. A Bath Knight is designed for bathroom use and needs to be wired in by a qualified electrician.
Personally I can't see how they work - if you have to SIT on the piece of material, surely when it's raising or lowering the person, the material is scuffing along underneath your rumposity? Or have I got it completely wrong?
You have to keep lifting up your weight to shuffle sideways as the band pays out to go down and shortens again to come up. You don't just need sitting balance, you need dynamic (moving) sitting balance and sufficient arm/leg strength. The one I tried had to be left unwound once the person was out of the bath to let the band dry and also had to be rinsed after use.
Notice that this youtube video is time lapsed and not a proper demo.