Rube goldberg project...

[nehalita]

I did one last year to change the batteries of a flashlight and have it turn on. I still have pictures of it actually (i think...).

As far as using heat, do you have a time limit for all of this to happen? If not, you could try melting ice to do something... ice is easily replaceable.
So if you have a net of some type with ice in it, and you melt the ice, the water can go through and add weight to a certain bucket that can then trigger another step. You can melt the ice by turning on a blow dryer or whatever else you might want to do.

hope it at least switches on a light bulb for you...