There are many examples of programming language runtime apps, such as

Scheme: https://itunes.apple.com/us/app/gambit-repl/id434534076

OCaml: https://itunes.apple.com/us/app/ocamlexample/id396515573

Python: https://itunes.apple.com/us/app/python-3.3-for-ios/id5779112...

Codea (LUA): https://itunes.apple.com/us/app/codea/id439571171

What restricts these apps from being awesome is that they cannot download source code or accept source code pushed to them from other apps. Cut-n-paste is the only way to transfer existing code.