There is untapped potential in the wireless signals generated by routers around town. Emergency responders around the world may one day use a mesh network knitted together from privately owned network routers as a means of backup communication, according to a recent study performed in Germany at the Technical University in Darmstadt.

Kamill Panitzek and colleagues used an Android application to sniff out wireless networks in a small rectangular area in the center of the city of Darmstadt. In the 0.19 square-mile area, researchers detected 1,971 wireless routers, 212 of which had public, unencrypted signals. In the event of an emergency making cellphone and data network service unavailable, emergency responders could use the wireless signals of homes and businesses to communicate.

"With a communication range of 30 metres (yards), a mesh network could be easily constructed in urban areas like our hometown," the team said, reported Phys.org.

Just as many routers have a “guest mode” that allows access without compromising network security, routers could be designed to have a channel designated for emergency responder use.

Results of the study were published in International Journal of Mobile Network Design and Innovation.

In a related study from 2011, Australian researchers at Flinders University developed an ad-hoc phone system called Serval that can relay VoIP calls between phones by using Wi-Fi networking. The system, which was developed with an eye on emergency responders, only works when the phones are within a few hundred yards of each other. Also, the call quality is poor, reported Ars Technica.

Phones in a Serval system can also act as relay points, theoretically creating a bridge between distant callers in the event that cellular service is unavailable. The software is open source and freely available for download.

A demonstration video of Serval featured by ABC News can be found on YouTube.