What you're talking about is simply collecting dew, a viable means of obtaining water IF the humidity and other conditions are right:

http://www.theweatherprediction.com/habyhints/9/

US Air Force survival gear for pilots contains a sponge specifically for this purpose- you sop up the dew and squeeze the water into your mouth. I saw this on Mail Call on the History Channel.

I bought some compressed sponges at a janitorial supply and carry one for this purpose. It weighs next to nothing and takes up very little room. Of course, a piece of cloth works, too. For example, you could take off your boots and walk sock footed through the grass, then wring out your socks. Personally I hope I never have to try this!

http://www.save-on-crafts.com/comsponbrmir1.html

A solar still relies on essentially baking the moisture out of the soil in one spot until the moisture collects on the underside of the plastic sheet. This is a different principle, I believe.

The above is my understanding of these two things, but I've been wrong before, so feel free to jump in with any corrections!

Bill