There's a new anemometer available for your iPhone:
This is a proper on and not just an app. It plugs into the headphone jack and will give wind and temperature readings.
It looks like a good bit of kit and almost certainly better than the apps that use volume to measure the wind. It would be much better if it had some sort of pressure sensor too to give barometric pressure readings or better still compute density altitude. I know you could get this via a data signal but your not always near a data signal when shooting and it would be much more convenient if it were built in.
I think I'll be sticking with my Brunton ADC for now. Also, I can't seem to find it available in the UK at the moment.
Could be potential for integration into one of the Ballistics Apps too?