I've wondering if the use of a hot-wire anemometer such as the $17 Modern Device one could be an alternative to pitot tubes:
I've done some research and according to (http://www.kanomax-usa.com/news/HotWire_vs_Pitot.html) the thermal anemometer could be an alternative to the pitot tube below 5.000 fpm (91km/h).
And here some discussion on the calibration:
I guess there are other factors into consideration such as the response time, temperature dependency, etc, but for lower speed airframes it may be a viable alternative.
if a waterdrop/snow/slush/flake temporarily cover a heated pitot, It does not cause problems.
With hot-wire approach I am thinking of two issues
1: if the sensor is hit covered by a waterdroplet (and cooled) - teh IAS will increase.
2: climbing up from a cold valley at -15C , hitting warmer air at maybe 0degC : (any additional sluggishness in thermometer would make it seem like airspeed is much higher..(and I would not like to have higher IAS than real during climb)