yes.. a way should be there..but we don't know (..yet)
1) if you want your device stop looking for wifi you have to go to advanced setting in your Smartphone and change it there, usually people don't do that, or yes?
2) No guarantee, yes like also can't be sure if people walk with wifi-on or using Smartphone or Smartphone+Tablet, but it could give us a reference..
AnaldGupta, the shop has wifi for customers, I was thinking about "something" easy to put anywhere to count people..
thanks very much for helping..