My friend has the hand held version Homedics Shiatsu Massager (SM-200) - purchased 3 years ago from a car boot sale (�10). She suffers from fybromyalgia which causes painful fibrous lumps at known trigger points. Vigourous massage relieves the pain & helps to break up the lumps to prevent future pain. She has used this machine to successfully massage these trigger points by placing it behind her back when sitting in an upright arm chair. It's a quite fierce pinching action that really gets deep into the back muscules.
We regularly see this version at boot sales & usually asking between �20 - �35. Knock the price down unless you can see it working in situ, it's too much money to risk it not functioning. Reputable sellers will offer contact details in case of problems. Hope this helps to make up your mind.