Facebook application

Hello I'm not sure if this is possible, but I want to have a facebook application to count the number of minutes you spend on Facebook. So, this needs to be a facebook app, not a browser plugin or desktop app. The counter doesn't need to be 100% accurate, meaning that if I spend 10 minutes on FB, it's ok if the app shows 11 or 12. There's an extra if you could do something similar for twitter (although i don't think it's possible). Thanks!