air speed sensor for rc plane

[Greg Needel]

i am helping a friend with an autonomous plane project where he is using an array of senors and completely control the plane. The only major problem that we are finding is figuring out a good way to do air speed. Most major aircrafts use pressure but for low altitudes this will not be accurate enough. other sensors use a heated element but within the confounds of this project for low power consumption and layout that wont work either. we have been playing with ideas with strain gages but are looking for an easier solution. any help would be appreciated.

requirements
low amperage draw
small (less then 2 inches)
low weight (less then 1/8th lb)
proven technology (we arn't trying to re-invent the wheel)

any ideas?