Bluelog is a Linux Bluetooth scanner with optional daemon mode and web front-end, designed for site surveys and traffic monitoring. It's intended to be run for long periods of time in a static location to determine how many discoverable Bluetooth devices there are in the area.
While there are many different Bluetooth scanners available, none I found did exactly what I wanted, most seemed focused on pulling down various bits of information from the target devices (like SDP records). I was also having trouble locating a scanner that didn't have a UI of some sort, which was a problem since I wanted to scan continuously without user intervention. After trying out all of the Linux Bluetooth scanners I could find, I eventually decided to simply write my own.
The more time I spent on Bluelog, the more features I worked into it. Eventually, Bluelog started evolving into a considerably more advanced tool then I initially intended. Still, all of the advanced features are completely optional, and if you chose it can still be used as the simple little scanner it started as.