A new app for the iPad called Codify allows users to code and then run custom apps directly on the device itself. Using the Lua programming language, Codify features a touch-friendly coding interface with plenty of pre-loaded assets, instructions, and example apps. Being able to both program and execute code using software from Apple's app store is relatively new, since Apple used to prohibit such apps.
There are still walls on this garden, however, as programs still need to run within the Codify app itself and cannot be shared with other users. The developer, Two Lives Left, has submitted an update to allow just that, but no word yet on whether it will be approved.
You can check out a video of Codify's features below, or head to iTunes to download the app for $7.99.