Someone where I work setup a similar app, only telling 3-4 people. Then, they built some really creepy/invasive stats into the service/page, too.
Just some advice: for each feature you add, make sure you consider how creepy/intrusive it is first. Nobody wants to be the person to object to something like this and, frankly, they shouldn't have to be.
At our hackerspace, the washroom situation was terrible. I found out there are some fuel cells that react to hydrogen sulfide! We thought about displaying whether or not it was safe to enter on an LED scrolling-message sign.
Just some advice: for each feature you add, make sure you consider how creepy/intrusive it is first. Nobody wants to be the person to object to something like this and, frankly, they shouldn't have to be.