Method to track visitor count on an Intranet page without using external providers

Question

Since most visitor count services are based on measuring public sites I am not able to use such services.

My goal is to measure how many unique visitors are surfing on a specific Intranet site per day. The problem is that I have very litte technical possibilities since I was provided with a simple IIS web space. This means that I can only use HTML5 and JS (This site will only be accessed by iPads). Maybe there is a new HTML5 feature I am missing?

Thanks for any tips and hints.