And we thought you'd never ask =)
Although documentation on the plugin itself is still far more sparse than I'd like, there is a standard playback-and-record tool available. This is what we've been using to make all the examples/demos you see online:
http://leapmotion.github.io/leapjs-playback/recorder/
It's pretty simple and easy to use.. record, crop, play. It packs up frame data in to a custom JSON (stripping keys) and the gzips. Still recordings can get large in size fast, but we're experimenting with a few things, such as being able to reduce frame rate, represent floats in binary, or maybe one day stream data.
I've added your github handle to our leapjs-skeleton Github Team, which should give you access to the private repo:
https://github.com/leapmotion/leapjs-playback
Feedback welcome, of course.
Cheers