Temperature switch

[BrianG]

There are several different ways to go about it. The thermistor is the best way, but you could use a small transistor as the temp sensor as well, it just isn't very linear.

A FET is probably the best way to do the actual switching, but you could get away with a smaller one as long as the drain-source current and voltage ratings are adequate. Since it is in switching mode, and not switching often, there is very little wasted heat because the only losses comes from the rdson value. Heck, a single ESC FET would be fine and small enough. The adjustment pot in the linked diagram could be a tiny PCB mount version.