The Shake Weight is a real product

A stretchy bracelet with a couple of "power balance" holograms on it? Which will "increase your flexibility and balance, improve your strength and overall over-being? [sic]"

Power Balance is the company that designs those bracelets that do just that. The products contain some components called holograms made of Mylar. It supposedly improves user body's flow of energy through the body by aiding those particular frequencies and increase cell communication. An alteration in body's energy field could have an alteration in perception or balance. Thus helps body in flexibility, balance, coordination and total wellness.

Good grief. Recommended retail price fifty bucks. Actual production costs: less than fifty cents. Effect: rather less than nothing.