source: http://news.spatialdev.com/portable-open-street-map/
The team is just getting started and you can follow along with the action here: https://github.com/AmericanRedCross/posm
Digital Democracy is working on something similar
http://www.digital-democracy.org/blog/open-maps-for-everyone/
just_testing explains the importance of it:
There are offline OpenStreetMap clients, but there aren’t ways to update said map offilne, or to create “mini-OSM” that later can sync with the main one.