There are several very capable, full-blown dev environments available for the iPad and iPhone. I think the main ones are:
Codea for Lua
https://codea.io/
Pythonista for Python
http://omz-software.com/pythonista/
Continuous for .NET
http://continuous.codes/
Codea and Pythonista also provide XCode templates you can drop your code into to create App Store apps from your projects. Not sure about Continuous.
Apple allowing iCloud syncing for code has removed the last real source of friction I'd had using Pythonista. Now I can write a script on my iPad, then reach over and run it on my phone, then if it's cross-platform sit at my Mac and run it from there too before checking it into Github. No fuss, no bother.