Its basically like a particle cache, but for any arbitrary mesh. We found it was getting unwieldy to do versions with cloth, especially if we had a scene setup for rendering, importing/exporting cloth sims into that hero setup got pretty ugly.
The other major advantage of our system is it saves out per-frame (or per sub-frame if needed) files rather than a single monolithic file, much easier on memory, much more renderfarm friendly too.
From my limited understanding it wouldn't be terribly hard to write, but its applications are endless. Anyone wanna volunteer to do an open source version? 
-matt