Hi Pat!
ChiP is ChucK compiled for the iPhone so it's not an app you download. It's more like an SDK you'd import into your iOS project to build an app that uses ChucK. There currently isn't an official" ChiP repo, but an easy-to-integrate ChiP project is something that's on the TODO list.
Some iPad-good news:
1. You can compile the MiniAudicle project (
https://github.com/ccrma/miniAudicle) to run on iPad. This requires having a Mac and having a developer account so you can provision the device for installing developer builds on them.
2. Still in the works and stealing Spencer's thunder, but his PhD dissertation is about making a more "appropriate and natural" interface for using ChucK on the iPad. More info here:
http://spencersalazar.com/auraglyph/
3. As Ronan points you, there are plenty of OSC-enabled apps on the App Store. You can download those and configure them to send messages to your computer and have ChucK consume the data from those apps. Unsure if any of those apps support ChucK talking back to the iPad though; I only ever did iPhone ~> ChucK on a computer.
Hope that helps! Let me know if you have any more questions.
mc