Here's an IC used in some alarm clocks that uses the power grid's frequency, along with a list of products that use it: https://www.radiomuseum.org/tubes/tube_lm8560.html

It was mostly used in the common radio alarm clocks, the ones with a 4digit red 7 segment display that were all based on an IC from the 70s that handles everything (minus the radio which is a completely indipendent module).