Yes, I have reported some bugs to the fsync() developer last year. I got a response a while back but nothing recently. It's been a while since any updates were released, so I don't know if he is working on fixes.
I did some napkin math:
• 20,265 active (v0.14+) users (source: https://data.syncthing.net/)
• Assume ~12% of them have iOS devices (source: IDC)
• Assume of these 2,431 users, ~10% of them would purchase a mobile app (source: making it up)
• Of those 243 users, each pays $9.99 (fair price?)
• Of that $2,427, dev keeps 70% (Apple's cut)
• Profit: ~ $ 1,700
I guess it isn't a lot of money. But depending on developer's skill it could be a (slightly) rewarding, fun project.