Playing with Navigation Timing https://dvcs.w3.org/hg/webperf/raw-file/tip/specs/NavigationTiming/Overview.html
I've been meaning to do this for a while but after Google Analytics launched their _trackPageLoadTime and it was useless on low traffic sites I decided to take a look.
Collecting data on the client side and sending it to nodejs which writes it to MongoDB. New collection perday.