For cops and firefighters, being wireless isn't just about walkie-talkies anymore. An increasing number of emergency workers rely on high-speed wireless data networks while on the job. But many of these networks are set up in a hub-and-spoke configuration: if a hub, such as a wireless base station, goes down, the network fails. This summer, Belmont, CA's PacketHop will release software designed to prevent that type of failure. The software enables standard Wi-Fi-equipped laptops, PDAs, and other devices to form their own "mesh" networks and share video, photos, messages, and location data. With the technology, emergency workers at a disaster site can "set up a network on the fly without the need for infrastructure," says Michael Howse, the startup's president and CEO.

In a mesh network, each device operates as a node, capable of routing data to several other devices on the network -- and the network survives even if several of its nodes fail or disappear. With PacketHop's software running on their portable devices, public-safety officials can, for example, view video streams from vehicle-mounted cameras. They can also instant-message each other, annotate or draw on images or maps in real time, and track each other's locations, provided that their mobile devices have GPS chips. The system can't handle voice data yet, so first responders who use it will still need handheld radios to talk to each other. But Howse says that, by providing an alternative means of communication, the mesh network should prevent the radios from getting overloaded during a major incident like a riot or a terrorist attack.