The basic idea is called wireless mesh networking, and the Wikipedia page[1] lists a lot of relevant research. The big problem with getting it deployed, though, is getting the software onto the phones. (Also, if you really do mean chaining signals across the border, you're going to need signals other than WiFi or Bluetooth to deal with expanses of untracked wilderness or desert between borders and population centers.)

[1]: http://en.wikipedia.org/wiki/Wireless_mesh_networks