Getting real-time browser data

I am planning to write an application that utilizes real-time browser data from all the browsers on a particular macbook i.e. the program should be able to know the specific amount of time a firefox browser has been on google.com and the amount of time that the safari browser has been on yahoo.com, the program should be able to tell when the google.com window has been closed in Firefox etc. How do I go about getting this data from the macbook, is there any location where real-time browser logs are stored in the mac?