Ask HN: Javascript mouse tracking library

I'm working on a project that involves tracking mouse movements on a webpage, and submitting them to the server for playback on another computer. I've been looking around but can't seem to find a good javascript library for the job. There are a few older examples written in Prototype, but I'd prefer to use JQuery or just plain javascript.

Ideally I'm looking for a method that will take very little bandwidth (i.e. quick to submit to the server), and will POST back the results in near-realtime. Before I go ahead and write my own library from scratch - does anybody know of an existing javascript source which could be extended for this purpose?