Neat video i stumbled across on youtube, video camera mounted on the wingtip with yarn on the wing. you can see the stall start at the root and then come out to the tip. neat-o.
The yarn reminds me of past discussions of lift differences on the top v. bottom of airfoils. A little more involved than the yarn, it seems like somebody could put some flat piezoelectric sensors on both surfaces and get a good measure of actual pressures.
i had a professor in school who was experimenting with what he called a "flush air" data system. basically static ports laid out on the top and bottom of the wing, so essentially the flight condition of the wing was continuously monitored in flight. Very easy to tell where you were operating along the Coefficient of Lift curve.