I have this effectively-infinitely-fast temperature control gizmo that I've been dying to make a good demo for. The gizmo produces a volume which is essentially immune to external thermal forcing, and that's what I want to demonstrate. The idea would be to show what temperature does to some unprotected thing, then turn on the controller which will make it completely immune.
I'm thinking of building a sort of thermal Theremin with a crystal oscillator beating with an LC. That ought to give a nice audible woo-woo sound when I heat it with a hair dryer or a small heat gun. I might try dividing the XO down to 10 kHz or so and using a sample-hold to do the downconversion, so that the signal would never leave the audio range.
That will sound interesting, but might not be the most compelling demo.
(Sorry for the teaser--I'll happily say more about it when the patent has been filed.)