Here is an interesting idea. Handcuffs that unlock via a timer and not a key. I don't think this is good in terms of the simple fact that you can never tell when you absolutely need to get free from these things. Say for example, the house catches fire..... Still the fact that these do exist is interesting.
handcuffs with a timer, the timer can be set from 1 to 99 minutes, at the expiration of the time handcuffed avtamaticheski open. speakbuy.com - eBay ()
This handcuffs have an opening bid of $290 and a 'Buy-it-Now'price of $500 (Plus $125 Shipping) and are currently on sale on eBay here.
You can see a video demonstration of these cuffs here: http://www.youtube.com/watch?v=hTX8wo8-ZkI
As with all things, use at your own risk... I have no clue if there is a back door to open them or not.