Dealing with IEDs
I'd earlier posted an idea for dealing with IEDs. The detonating mechanisms often use cell phones, or sometimes walkie-talkies. All radio receivers also emit RF radiation to a small degree, and cell phones periodically send out a short signal (so the system knows where you are). A device to detect this could be quite useful. Even if short-ranged, (1) range can easily be extended by several factors by use of a directional Yagi antenna, which also would tell you whence the signal came, and (2) you could put the detector on a small remote controlled car to sniff around. It could not only scout for you, but also be useful sniffing out buried or hidden IEDs, in a way that's a lot safer than digging for them.
Just in case anybody from DARPA is reading this, they already had cell phone detectors. Here's one, and here's another. I believe a similar device could be designed for walkie-talkies, albeit of shorter range. And mass produced for a fraction of what's being charged here.
They make you turn cell phones, and computers off, on plane for just that reason. They radiate radio frequency signals, even when not transmitting.