The switch doesn't require any power it uses energy harvesting technology. I haven't tried it for myself yet but it seems pretty promising. IMO I would stay away from the RadioRa for only one switch. It will be very expensive and you have to buy the repeater in order to set it up.
I skimmed through some of the material printed about these devices. Pretty interesting. One problem might be that the receiver(relay) can't be installed in a closed metal box. I guess they'll work in plasic boxes thogh.
