I am using it to measure the flow rate of the liquid cooling system in my PC. If the flow level were to drop below a certain level an alarm will sound and an LED will flash on the front of the case.
This is just part of a much larger project. I made this tutorial because there were some threads about using this sensor over on the seeedstudio.com forums. So I thought I would post it here too. I also put a link in the playground to this tutorial on my site.