GoTenna

Well, Holmes, from the range, it appears to be a point-to-point radio rather than an ad-hoc network. The length (6 inches) favours the 40MHz ISM band, with a low-gain integrated antenna & low data rate. I daresay the device casing itself could serve as the radiator. Perhaps some proprietary signal encoding for the (very) low signal power & to handle multiple access. Hardware is probably FPGA-based DSP + ARM processor. Most of the communication smarts would be at the TCP/IP level (e.g; retransmission) rather than in the radio per se, enabling low power operation.

It's nice to see a small start-up build something like this.