A modern programming language that makes developers happier.

kotlinlang

If you don't need the MAS then Conveyor can do this. It cross-builds for every target from your laptop. Unfortunately, we don't currently support making uploads to the app store. It's on the todo list, but unless you want the integrated billing or discovery out-of-store distribution seems to work just as well (Conveyor makes a download page for you, provides sparkle updates and other things you'd need).

Conveyor seems expensive for an independent developer. My app is not open source

Interesting, first time we got that feedback. There's a formula on the pricing page - it's about a day's worth of labor costs. But if it will save you less than a day of effort/learning a year it wouldn't break even. If your app  is mac only, there's less value.