The Department of Homeland Security has unveiled a new two-way radio replacement system for firefighters that’s designed to work in extreme heat and disaster situations–and is disposable. Centered on a new, coin-sized router called WISPER, the communications system is designed to work in places such as collapsed buildings or smoke-filled houses where radios often fail.

WISPER is a tiny, one-inch square disposable router that is waterproof and heat-resistant up to 500 degrees Farenheit. Each contains an integrated two-way digital radio, antenna, and 3-volt lithium cell. The devices were developed for the DHS by Hawaiian firm Oceanit Laboratories and the University of Virginia’s Department of Computer Science.

When used in fires and other disasters, WISPER routers leave digital “bread crumbs” that track firefighters’ locations. Users are intended wear up to five routers simultaneously by carrying them in a belt-mounted waterproof dispenser. Firefighters who venture behind concrete or out of radio range then drop a router out of the dispenser as a location marker. Dropped routers then form nodes in a mesh network that will automatically reconfigure even if the bread crumbs are moved or destroyed. According to an Oceanit representative, “if a WISPER note is damaged, the network reheals or repairs itself in real-time to maintain communication.”

The DHS sees use of the devices as an alternative to traditional two-way radios or walkie-talkies. WISPER is integrated with two devices already on the market. One, called the Physiological Health Assessment System for Emergency Responders (PHASER), is a combined body temperature, blood pressure, and pulse monitor. If the PHASER monitor indicates that a firefighter is in danger, their comrades can then be led to them by the bread crumbs. The second device is a netbook-sized integrated microwave radio/battery/navigation device called the Geospatial Location Accountability and Navigation System for Emergency Responders (GLANSER). (As always, the Department of Homeland Security loves acronyms.)

WISPER uses a low-power, slow communications protocol called ZigBee with a maximum speed of 100 kbps/second. But, according to Jalal Mapar of the DHS, that is enough: