I'm looking for ideas for a shared calendar system with a car that is borrowed by a few different people quite regularly. Unfortunately, NYC camera ticketing being what it is*, people tend to get many tickets without knowing, and it's tough to try to figure out who had the car at the given time of the ticket.
What I'd like is a system that the borrower can quickly and easily (like within 15 seconds) mark when they borrow the car, and when they return it. Perhaps scanning a QR code that creates an event on a shared calendar? I'm thinking that if it is more time-consuming than scanning a code, like perhaps typing on a shared spreadsheet, then people might not do it because they'll think, "I'm in a rush, I'll do it soon," and then forget to do it. But if it's really quick, then they won't push it off.
*I say this just so Dan can link to the "Why the heck are you living in NY?" thread and give him that sense of pride and superiority for the day.