The sample code for the blog post Getting To Grips With The Core Media IO Camera Extension, a 3 part series, part 1 of 3: The Basics: creating an installable Core Media Camera Extension and its container app, from The Offcuts.
You can also check out the sample code for part 2, and the sample code for part 3. They are all iterations of the same CMIO Camera Extension, with an increasing featureset.