Whether the Gypsy Sit Upon will help with your back problems is dependent on the problem. I personally benefit from the gadget. I have 3 of them. One at work, one in the car, and one at home for when I have to sit for any length of time.
If you are wondering if they will help your back see if you can borrow one from someone to see if it helps. I was at a quilt retreat and in considerable pain when one of the ladies brought her sit upon over and said "try this". Within 5 minutes I knew I had to have one. I have loaned mine out many times, some like them, some do not.
It does take a little while to get used to balancing yourself. Your abdominal muscles may say hello, but that's not a bad thing.
Aileen