See the latest keg monitor data from an “Internet of Beer” project created by Ted Alonso. While not super active at the time I scraped this screenshot, it’s a handy demonstration of a postcard project page with data collection.
The metrics are stored in an attached open source document-oriented database system, MongoDB, available as a Heroku addon. The Heroku application also serves the page which you are currently reading. Every 5 seconds, this page queries the Heroku API to get the temperature for the last 8 hours and pours per day for the last 2 weeks using MongoDB map/reduce functionality to aggregate the data.