Dear,
The current version is ready with some restriction. We can't check the actual number of cars on the parking, also the parking entrance must be paid before (fixed price) not in dependence on the parking time. Maybe there are some other restrictions resultant from your requests.
To get know more about this component you can read the documentation:
www.artio.net/joomla-extensions/electronic-tickets or try it on our demo site:
demo.tramin.artio.cz/joomla15/cs/instructions/vm-eticket
Also the version for Joomla 1.7 will be available soon, with no connection to VirtueMart.
In dependence on your requests we can modify the component by your wishes as a paid support.