I just saw the commercial for this thing. It is an actual air guitar. It shows kids happily prancing down the street to the obvious delight of all around them. The promotional material says "Your young musician will thrill at what they can do with these magic gloves. They can play alone or with others."
The wonderfully named "Hand Band" will not do any of the above. The noise created by the device would more likely cause running and screaming. I would wager that unless your child goes to school on the short bus, they will be doing this alone. The only purpose I can see for this thing is to create a new generation of super mimes that add grating electronic sounds to their performances.
Please, if you don't want your child to hate you forever, do not buy this for them. At nearly $100, this would likely be the "big present" for a lot of households. Don't squander it on this monstrosity.
I have found it helpful to do the stretching exercises my physical therapist recommends. Do some core strengthening exercises, such as the ones highlighted at The Mayo Clinic. By keeping your core strong, your back won't put itself in a position to cause that sciatica pain you are having.