The idea is a small ball that you throw in with the food. It warns you when the temperature gets too high because nearly all water boiled off or the fat is close to its boiling point (two separate models). It won’t save your food, but it will save you the scrubbing and/or kitchen painting.

The simplest version would be a wax based mechanism that pops once when it gets too hot, like the turkey poppers. Instead of just popping it would have to make a loud *bang* though. Advanced devices could make extended sounds or other alarms. Bluetooth probably won’t work from inside a pot because of metal shielding. Ultra sound could penetrate the pot and reach a receiver outside.

Even the simple devices are reusable until they go off the first time (can be washed like all other kitchen utensils).