thread This is basically my new job.
I work for a startup providing a map of charging points across Europe, and you can see the current status of charging points (available, occupied, offline, etc) and start/stop the charging as well as pay through the app.

Most of them charge per minute or per kWh but some are free.

I'm not sure about ZipCar but there's a similar service here in Berlin and they have their own depot where they can charge the cars when needed but they do use the public chargers too.