There are 132 reviews on Amazon here:
http://tinyurl.com/ydb824x9
Exactly half of those (66) give the product a 5 star rating but it's important to note that a significant number of the other reviews rate it as worthless.
A separate Amazon listing has 211 reviews. Once again, most of the reviews are positive but there are still plenty of people who see the product as a total waste of money:
http://tinyurl.com/y6wjogom
It does nothing that putting a 2p coin in your shoe would not do equally well, if it does anything at all that is!
I am reminded of the magnets that women were supposed to use to cure PMT. The same result could be obtained by putting two fridge magnets down your knickers, but at a cost of a few pence rather than £28 each !