Check one out at your local gym. I go to a gym with a client and after her workout she uses the vibrating pad. The idea is to use it after exercise (you don't stand on it, you squat) As Prism99 said it stimulates nerves/muscles and helps with balance. It is quite powerful and you would need to use it carefully, with supervision.
I am a firm believer most exercise equipment bought for home use is a waste of money, at best they end up as expensive clothes hangers or end up stuffed under beds. Go to a gym, get a personal plan made up by a professional trainer. They have up to date equipment, they are very safety conscious and many are cheap (YMCA), it is a great way to meet others, all shapes and sizes (no embarrassment) and a good way to stay motivated.
I work in disability support and to be honest despite what you may think, gyms are one of the best places my clients gain acceptance/make friendships...from young people through to seniors.