I have got a cheap candy-land made doorbell that's operated via piezo crystal switch (non-battery, non-power-line) and 433MHz freq. It has some melodies and vol

I have got a cheap candy-land made doorbell that's operated via piezo crystal switch (non-battery, non-power-line) and 433MHz freq. It has some melodies and volume built-in, The design is simple and easy to hack (and build something else). There are rather cheap light switches that operate on the same principle and can be used.