This is a digital thermometer with a sensing probe. These are good for attempting to measure cold/hot spots. This unit isn't that great because it takes a reading about every 7 seconds, so you have to wait for a reading. I've wired a switch onto this meter so it won't always be on. A backlit meter that takes readings every few milliseconds would be ideal for paranormal investigations, like my new temperature monitor.
Schematics to build a temperature meter are available in the How-To section.