Tracking how many people look at your products is an expensive thing to do. Sony has a system that tracks people in stores and detects where they are looking and for how long, but expect astronomic prices.
Xuuk is offering the Eyebox, a pinhole camera that connects to your PC through USB2. Install some software and voila it counts the amount of people actually looking at the product / advertisement up to a distance of 10m away. The software links into Google’s pagerank technology for revenue models on a how many times your product was seen and gives you loads of statistics. And this for only $999,-
Using this camera you can measure or track how many viewers your poster has.