I have a couple of good friends working at a company called Meraki Networks (http://meraki.com/). They are developing low-cost mesh wireless routers. I know they are actively working on a solar-powered version, though it seems like it hasn't been generally released yet. I'd be happy to connect you with them; in general, I think their approach is a good match to the global health needs.

I am told they their solar powered node is in beta testing right now. They plan to release it this fall. Obviously, it does include a backup battery.

Overall, the thing is truly wireless -- you don't connect it to anything. Pretty impressive.

In Malawi we have built a fairly long distance wireless link using off the shelf equipment.

A rural hospital was in need of connectivity so we welded together an 18 meter steel tower and put it on a nearby hilltop. We then added an off the shelf 48V windmill to power 4, 12 volt solar batteries. Finally we put a mikrotik router with one 802.11 radio pointed at another health center 30 kilometers away (which also uses mikrotik routers), and another one pointing down to the hospital. We used a DC-DC converter to go from 48 volts to the 12 volts needed by the mikrotik. We used wind instead of solar simply because we had a windmill on hand and the location was consistently windy.

I'll try and post some pictures. I am happy to go into more detail if people are interested.

Meraki Solar is shipping now:
http://meraki.com/products_services/hardware/solar_overview/