SwiftGoo is an open source example from Simon Gladman providing a simple tool with a Goo like image effect.
SwiftGoo is inspired by the Goo effect in Kai’s power tools from the early 90s and uses a Core Image warp kernel to move pixels based on a user’s touch.
This video shows SwiftGoo in action on the Mona Lisa:
You can find SwiftGoo on Github here.
You can read more about how the effect was created in just a few lines of code using CIWarpKernel on the FlexMonkey blog.
An interesting use of Core Image.