[tgv]

Also not great for higher voltages and power.

[idiotsecant]

You can in fact purchase right this very moment bimetallic temperature switches for nearly arbitrary voltage / current combinations.

[Turing_Machine]

Right.

Mouser (a general electric/electronic component distributor in the USA) has 'em on the shelf rated for 600 V, 50 A.

I'm sure that specialty distributors offer a much wider range.

[Pathogen-David]

I've opened up my water kettle before and it uses a little bimetalic strip to shut itself off once the water is boiling. According to the label it sucks 1500 watts and it's just shoving mains voltage through the heating coil.