This seems like a good idea on paper but I wonder how many people will actually bother to buy them considering the quite large initial outlay? Energy efficient light bulbs are still not that popular I believe and yet they cost about two quid and pay for themselves in just a few months. Will people consider buying something that costs £20-30, needs batteries and may take a year or two to pay for themselves (depending on how many things you leave on and how many locations around the house). Not in large numbers I suspect….
I turn everything off in my house anyway, even down to turning my cordless phone off when I go away for a few days. Not that anyone ever phones me anyway (except my mum)….