This overlay app decodes CCIR 5-tone SelCall chirps and displays them on the screen.
Source code and app download here: https://github.com/Nosen92/F4HWN-app-ccir-selcall-decoder
How I did it: I recorded my 433 MHz keyfob and inspected the signal in Universal Radio Hacker. I found that all commands were fixed code, made of 8 bytes each, sent with its complement, all of it Manchester encoded. So I vibecoded a little app, transferred it with UV Studio to my UV-K1, and now I can lock & unlock my car with my radio! Will post source code on github once all my bugs are squished and the code is de-vibed (if there is such a thing), it's still kind of flaky, hacky and proof-of-concept-y.
Update: Source code (without my car's secrets lol) is available here: https://github.com/Nosen92/F4HWN-app-keyfob