A "fuse" for overvoltage
It's a bit of a hack anyway. Best option would be to identify devices that do not support 220V and wire a different plug only available on your converters.

You can get a varistor.

This is a component that starts conducting above a certain voltage.
As seen here with the blue line, above +/-300 volts, current will quickly rise.


You must use a fuse or circuitbreaker in series with the varistor in order to disconnect the circuit when the varistor is conducting. You also have to use a varistor rated for enough power to prevent the varistor to blow before the fuse. Many devices will already contain varistors to reduce the effects of transients.

Beware, varistors can explode violently.

Another option would be to use a voltage monitoring relay. These are more expensive, but are less destructive.