Battery FREE wireless mouse

Last nite I was surfing in a hardware shop, looking specifically for some USB mouse, wanted to avoid wireless as it requires batteries, and there I see this new innovative product it is a wireless mouse which don't need battery at all...at first glance I really picked up the product, Than was wondering why they are giving this mouse pad, and yes there is some wire inside, why it is for ? Than saw a demo of it ... okay it is battery free, and very light weight also, but catch is, it works only on the mousepad which they give, and this mousepad needs battery from your USB port, So it is actually battery FREE wireless mouse, BUT dependent on mousepad :)