Release Method #72: Baking your keys in the oven...

This one is a little on the risky side, but then so is self bondage.  Set your keys on a baking sheet and turn the oven on to around 450.  Once the oven reaches the right temperature turn it off and finish your bondage setup.  Now you'll have to wait until the oven temperature reaches a touchable temperature before you can pull the key out and release yourself.

Of course opening the door will speed up the cooling process, but it would still take a while to cool.  Using oven mitts would be fairly difficult with hand cuffs on.  And you'll probably want to put all of the tongs in your house out of reach.

There are of course many variants to this idea.  Most oven models have timers on them to turn off the oven after a certain period so you could extend the duration.  You could also use the "self-cleaning" mode of modern ovens which physically lock the oven shut and heat up to about 600F.  This process usually lasts about 3 hours.  You'll want to test this with your keys first, but you should be fine as even aluminum melts at well over 1000F.

I've even used a big pot of boiling water to trap a key.  With the pot moved to the middle of the living room and only one free hand available, I couldn't move the pot or empty it without spilling a massive amount of water, and I couldn't reach the key until the temperature fell to the low 100's.  It's a little more involved of a setup, but the idea is still the same.