Biopay
Biopay is a software system to operate a biodiesel cardlock for a group of people.
Biopay interfaces with a CardMaster™ Cardlock over a really long serial cable. It stores everything in a CouchDB. Biopay has a web application component, as well as background daemons to monitor the cardlock as well as other jobs such as payment processing.
If you'd like to see a demo of Biopay, go here: http://screenr.com/Yvls