NASA software engineer Al Bencomo of San Jose produced this very impressive example of what can be done by combining an obsolete or second-hand smartphone with open source software and auxiliary hardware. Not only does his robot automatically track and chase a rolling green ball, it avoids obstacles along the way. (Scan the embedded video ahead to 0:37 to see this behavior in action.)

Bencomo’s bot consists of the following major components:

He puts the total cost of the build at less than $400 including the (used) phone. The OpenCV (Open source Computer Vision) library does the heavy lifting on the software side. Extensive, detailed technical info about this approach to ABR (Android Based Robotics) is available here.