I have a Homedic back massager that I bought at Walgreens at Christmas time. I bought one for my husband also. My problem is mostly in my lower back and this massager has been a wonderful release from pain for me. My husband also enjoys his very much.
The one problem I have is that I am fairly tall so the upper back portion stops just short of where I need it unless I pull it up in the chair to a point higher than it is supposed to be, However, if I do that it will work nicely on tension in my upper back.
Also, with this particular massager it is important not to lean too hard on it as your back will be sore. Adjust how much you are leaning on it and it works fine.
I don’t know what model number this thing is, but it was labeled as a Shiatsu Cushion with Heat.