Feasibility of a Wi-Fi Positioning System In the project of guiding a sight disabled person in a known environment, we need to have a precise way of figuring out where the user is. Our current solution is to use WPS. 

This is however our first project with Arduino, and we're not quite sure if we're going the right way about this. We're thinking of getting a compass component and such, but is there something we should know before advancing further in the project? 

EDIT: Additional information. 
The system is placed on the user, most probably strapped to the arm. The communication to the Wi-Fi beacons will be done from there, as well as the calculations. 

The environment is supposed to be as complex as an exposition hall, but we can aim higher. 

Budget range is around $100, Arduino itself excluded. A UNO is already provided to us.
I don't think that arduino is the right hardware for such a project. Better use a cheap android phone, there you have a stronger processor with more memory as well as a lot of sensors like compass, accelerometer, gyroscope and maybe in newer ones barometer, which you will need - also you have wifi. An arduino uno just comes without wifi and all the sensors. Also I guess a lot of persons already have a phone, so this will lower your project costs, because hardware is already available at most users. Last but not least I think you could use mobile phone vibrations to give feedback to the sight disabled users, oder sound commands like "go left" etc.