currently it's python code using opencv machine vision library, both known to run well on raspberry pi.
pure cross-platform commandline tool, no gui.
-mouser
Great, I love cross-platform solutions

some unknowns:
issues regarding using a cheap raspberry pi camera.
-mouser
I don't have one of those, but have not heard bad things about the 'original' RPi camera, it seems to be quite reliable as there are several projects using them, even for recognizing the surroundings in semi-autonomous robots.
coding eventual GUI interface using touchscreen raspberry pi touchscreen.
-mouser
I have that touchscreen, but I still have issues with typing on it, even using the recommended on-screen-keyboard drivers, and also the screen-space is quite limited at
1280x800 800x480 pixels, even using a webbrowser is a chore

The touch-input for moving the mouse is comparable to a 7" tablet, but Raspbian Jessie is not yet very optimized for touch interaction
