For slow chairs, and close by, BT will be OK. Say for loading into a van, or moving one room to another.
For anything heavy, or faster, or further than about 50 feet I wouldn't trust BT alone. Esp bad if the antennas are low down or surrounded by metalwork as on a powerchair. Like driving up and down your street for fun. I think its too much. Most phone or embedded device BT is limited to and expected to be used under 10 meters.
Using my signal boosted/modded RC system, which are much easier to control than a phone by the way, I get around half a mile through buildings and cars etc in heavily congested built up areas.
And around 4 to 6 miles in the air. (Yes powerchair don't fly very well, but my Quadcopter and Airplanes do!)
See here:
http://www.wheelchairdriver.com/12x.htmWith a 2 watt WIFI booster added. Now upgraded to a 3 watt booster which is slightly "over run" to give around 4 watts RF output.
That's with a DSMX system. A high sensitivity encoded Transmitter/Receiver using dual channel, wide band, while simultaneously frequency hopping across all 23 channels. And using 4x receivers for better reception and in different planes (polarities), to also cover null areas/multipath errors etc.
The BM2 and BM3 use this system with 4 DSMX spektrum receivers in different places on the chair to be "seen" from all angles. inc one high up in the backrest where theres no metal. And one behind plastic rear lights.
And so no dangers/problems around the town a long way away, inside metal shelled vehicles etc. And huge range.
The problem with 2.4ghz today is that *everything* has decided to use the free band. Its so congested its unreal. E.g. Here alone in my own house, 2 phones, wireless network router using wide band, door camera using a wide band and on 100% of the time (high pulsewidth percentage), BT on desktop computer and laptop, wireless network on laptop, phones, and carers phones using BT and wireless, 3 chargers use BT to communicate to my PC always powered, my RC planes systems intermittently, even my gopro and my Nikon cameras use it to send pics to PC, and my vans OBDII is always on and left plugged in. Then there's the microwave which pukes out about 4 times more pure noise over the whole band, and a wireless repeater in the hallway... My alarm system (12 more devices), and a baby alarm I use to talk to carers. And almost every house is the same.
How many 2.4 sources in a typical street? Probably 100!
You need to have a strong secure setup for safe powerchair control, they are heavy, and will run into cars, the inside of your van/house or a person before the failsafe can stop it.