I was thinking about the Ocarina app, and how much it could be improved, when I though about another application which might not be able to be ported to Flipper Zero, at least not without some GPIO addition: LSDJ.
While I do like that there are so many RTTTL ringtones that were on RogueMaster's firmware from back in the Nokia days (Many of which need to be reorganized, renamed, and cleaned up by artist or genre), I think there is potential to port Little Sound DJ which has been used to do chiptunes in the style that could be done with the classic Gameboy. However, you don't need a Gameboy to use LSDJ. An emulator can be good enough.
At any rate, I'd though I'd bring it up. What do you guys think? Also, what other apps do you think should be ported to the Flipper Zero?