>I wonder if some fancy playing with ultrasonic sensors or maybe 
> microwave detector might work?

When Marco first posed the question I thought airport weather
radar. It happened that I'd recently seen one of those Mayday
programs about an air crash caused by a micro downburst

http://en.wikipedia.org/wiki/Downburst

and the subsequent introduction of Doppler radar

Maybe the scale is too small and the expense too large for wind
coming out of caves though

Remember the 'air density detectors' used in Alien ?

blip blip blip "OMG, it's right behind you !!!"

And The Simpsons Santa's-Little-Helper-In-The-Airduct sensor
of course, but I'm sure *that* one is just made-up
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist