None of these devices that stimulate muscle can possibly work. They contract the muscle, yes, but you do that yourself thousands of times a day. muscles grow when they are loaded to failure and broken down and rebuilt slightly stronger. To do that you have to introduce a load. Take an arm curl, I can lift a tin of beans 1000 times to no actual benefit in the muscle because it's well capable of lifting that weight, to get the muscle to grow I have to lift something heavy enough that I can only do it about 8 times max.
There are no short cuts!