Ask HN: Know of a good Anemometer (Wind Speed Sensor) for a Computer?

I am trying to monitor the output of our cooling system for the server room. I already have temp gauges, but would like a sensor to indicate when the wall unit is no longer blowing. It would give me a little more time to respond then the temp sensors.<p>I would like a Anemometer (wind speed indicator) that is able to hook via USB / Serial and be read by a UNIX (OpenBSD, OS X, etc.) box. Ethernet would be fine also. It has to be lightweight as I am hanging it off the ceiling.