I spent a fair bit of time over the summer getting set up and aquainted with OpenCV4Android, starting with the Android SDK itself, and also including the NDK for native C++ development.
It’s all quite a bit of a learning curve: You end up learning Eclipse, the ADT add-ons, the Android framework, Java, NDK, and OpenCV4Android all more or less at the same time – and that’s assuming you’re happy with OpenCV and C++ to start with. Anyway, I have got there with plenty of help from the web. (I also have my own set of notes, taking me through the entire process again step by step, which I have since done twice on two new laptops).
But I am now completely up and running on this environment, and have successfully ported a number of my own OpenCV apps to run on various Android devices. They run well, too – the processing horsepower available on a modern smartphone turns out to be more than enough to handle images from the on-board camera, and run ‘average’ OpenCV apps, and I am currently working on two such apps for clients.