Alien Scanners..Do they really exist?

[Starguard]

For all of you that saw part 2 of the movie "Aliens" (the one with the Space Marines in it). There was a part where they (the marines) had these small radar like scanners that penetrated thru doors and walls, and allowed them to detect any movement that went on within several feet from themselves. Does anythng like that actually exist? If so, where can someone find something like that?

[si_blakely]

The UK Government has installed radar based scanners (some sort of LF radar) that can detect a single heartbeat in the centre of a full goods truck. These are used to prevent illegal immigration through it's borders.

Similar devices are used by rescuers to find survivors after building collapse - probably with less success due to material densities and sub-optimal conditions.

Tom Clancy used the concept of triangulated Heartbeat radar as a military tool in the book "Rainbow Six." Of course, he writes fiction, but has a reputation for basing his material on real-world technology.

The problem (from a military perspective) is that if you are emitting rf that goes through walls, you may as well forget stealth and storm into the building with lights and being as noisy as you like - they will know you are coming and where you are. Your opponents will have jammers, decoys and detectors. Even poorly equipped terrorists may be able to tune a simple radio in to detect the rf, and know that you are coming, or rig a microwave to jam the beam.

The best solutions are passive (listening devices, CO2 and thermal detectors), or maybe external, static transmitters with portable passive receivers (like an AWACS transmitting RADAR for a flight of fighters to receive and process.
Or the external systems can process all the data and stream info (via low power frequency agile encoded datastreams) to people that can detect and decode it. You start doing this early, so there is no difference in the "chatter" when you do launch an attack. Also, the source of the data is constant (and diffuse). This is how battlefield data will be managed as more data is collected and disseminated.

Simon