This is a neat concept, though the details of making it a real solution are a bit more complicated than most people realize. For starters, a walking user of a Segway can simply step off , or pick himself up and walk away, if the machine runs out of battery or eats a gear mid trip. Not so for the paraplegic, he finds himself face down strapped to a useless contraption. On the medical side, most people in chairs have some degree of skin trouble from poor circulation and constant pressure on weight bearing areas. The advantage of sitting is that the primary weight bearing area is cushioned by the largest muscle of the body and a layer of fat tissue as well. Standing, this pressure load is largely transferred to the bottom of the feet, which are designed to transfer the load to muscle and connective tissue in the legs that do not function properly in the patient, making pressure sores very difficult to avoid and limiting the time that can be spent using the device.
There are a whole string of similar issues that designers, engineers, and medical experts will have to overcome before this concept could become a workable tool. I am sure that most can be solved, but doing so will almost certainly exacerbate this products other major weakness, price. The Segway, which has a much larger potential audience and considerably smaller likely liability concerns, sells for around $7000. This [products, cost would certainly be much higher. Considering that the average user would almost certainly have to have a backup chair for times when the battery on this is dead or it is in the shop, that’s a lot of money.
I would love to see it manufactured, but there are a lot of hurdles between here and that there.