I'm looking for a remote controlled lock. Or more precisely something like a latch or a deadbolt.
It will be for a friend's sons's "secret stash" situated behind a small bookcase on hinges, in a little brick alcove (God knows why that's there...). So there should be no keyholes or any sign of the lock outside.
Since this is a child's project I'm not looking for high secure things, of course it should fulfil the function of a lock, but the key is being battery operated, easy to install and reasonably reliable.
There is no need for many fancy functions, time locks, various users etc, just a remote controller and some kind of latch like thing it operates. 2 keys are needed or 3 tops.
It shouldn't be too expensive and should be available either world-wide, or in Europe or at least be bought online.
I've also though of RFID based solutions, but the wood is around 2 inches thick, not sure if that would be an issue, plus I don't want too much assembly and complications. Simplicity and ease of installation is a focus

I also don't want to hassle with electric cables because A.) I'm lazy, B.) It shouldn't be dangerous to the child and C.) I don't want to undertake serious modifications to the place apart from drilling a few holes and putting some screws in.
I hope some of you will have some kind of handy solution

Thanks for your help
PS.: this is the "unhinged" end of the bookcase and the other pic is the part of the wall which is next to bookcase.
Pics of the situation:
http://i.imgur.com/j0LN8FO.jpg
http://i.imgur.com/u9fJK7t.jpg
http://i.imgur.com/vHEMVpU.jpg