What do my pets do when no one is around? I decided to find out. My session will cover how (and then some).

A webcam and some JavaScript using WebRTC is enough to take snapshots, but the trick is finding the snapshots worth saving. I’ll share how to write an image diffing algorithm that creates a visual motion heatmap, which can be used to programmatically recognize when a snapshot has caught something happening. The interesting snapshots are then uploaded to Twitter for remote viewing.

Even modestly sized images can contain a lot of data in the form of pixels, so I’ll discuss how to lighten the computational load while keeping acceptable accuracy.

I’ll also talk about making this work on affordable hardware (Raspberry Pi, cheap Android phones), other potential uses for diffing and motion sensing, and some interesting/spooky issues I came across.