Inspired by this repo I have implemented a similar functionality entirely in the flipper zero
It uses the IR sensor on the Flipper Zero to gather entropy from IR sources (such as a lighter) to seed a random number generator. The idea is that fire and other similar IR sources are not predictable sources of data, and thus it can be a reliable source of entropy. Obviously the flipper doesn't gather enough data (unless you really like flicking a lighter near your nearly $200 toy) to get any sort of decent entropy, this is more of a PoC.
I am NOT responsible for any damage to the flipper or yourself! Be safe with fire, and be safe with your other entropic sources!
I am also NOT responsible if you generate insecure keys using this as a source of entropy!