The whole system is solar powered, and provides it’s own networking via the Raspberry Pi synchronisation node shown here. The android tablets also recharge from the same power source. The Raspberry Pi networking is a direct descendant of the experiments we carried out in London during the Sonic Bike workshop.
Here are three of the tablets syncing their data – photographs for people to identify each other (names are used differently to western culture), audio recordings of verbal agreements (a requirement in preliterate societies), and information of who knows who.
More on this free software project, links to source etc over at foam kernow.