Whilst a commercial offering is probably quite expensive, it strikes me as the sort of thing you could do quite cheaply and easily with an arduino. I've actual

Whilst a commercial offering is probably quite expensive, it strikes me as the sort of thing you could do quite cheaply and easily with an arduino. I've actually been collecting the vibration motors from disposable electric toothbrushes to build my own belt; as they were designed to run form a single AA battery powering them should be easy.