I remember a company in the USA making all sorts of claims about their vibrating beds. I asked if it would help my mum who had osteoarthritis. "yes sir indeed it will" was the reply. "Bo**ocks" was mine. Vibration doesn't smooth roughened surfaces in bone joints. That particular claim is spurious.
It depends on what is causing the back ache. The most usual cases are where there is movement between the vertebrae because of wear in the disc. This can become prolapsed, what we used to call a slipped disc. Some movements can cause this to pinch the nerve which is a very short and sharp pain but which mostly causes all the surrounding muscle tissue to become inflamed and it is that that gives that awful nagging pain which lasts for ages. No matter what you try to do, you can never get comfortable.
A vibrating bed will not solve the problem of the prolapsed disc. It may alleviate some of the effects of the inflamation but so too will anti inflammatories like Ibuprofen. You need prescription strength though and have to take the GPs advice because it can increase blood pressure. A hot water bottle is good and some of the vibrating cushions or pads may help. They are likely to be just as good as a bed. The aim is to get the inflammation down and that is in the area where the affected disc is. The rest of your body doesn't matter.
If you can work out what causes the disc problem in the first place, you'll reduce the number of instances. Mostly bad seating and poor posture are to blame. I'd buy a good chair before a vibrating bed, one with a high back that supports the shoulders too. Sitting slumped watching TV puts strain on the lower back. A good quality firm matress, but not too hard, will also help avoid future problems. People rarely change their matresses frequently but, matresses like shoes, become distorted and fail to support properly.
Those bags with cherry stones that you can heat up in the microwave are good for lower back pain too. Heat increases circulation to help the inflammation go down.