Not exactly a programming question but here it goes:
How can a company who is distributing passbook passes via email or web prevent a pass from being installed on more than one device?
I can not find anything about this on Apple docs. The only I can think of is to check on the device registration webservice whether the combination of pass type and serial has a device already registered and delete it , but I am not aware of any command to delete the pass remotely.
Another option would be to check if it is already registered prior to generating the pass but this would only work for URL distribution, not for email.
Is there any way to delete a pass remotely via push notification + update? Any ideas on how to solve this issue?
Mail and Mobile Safari will present any pass they are given and the user can decide to add them to their Passbook. There is nothing the pass creator can do to prevent it except to be careful about how the .pkpass files get handed around.
If you really only want to deliver a specific pass to a specific device you might consider a companion app that uses a custom API to communicate with the the backend and request the pass for that device that way. Then you have much more control than distribution via email or url links.
Apple frowns on trying to delete a pass programmatically; only users are supposed to delete passes because they added them. You can, however, update a pass to make it clear that is not valid and should be deleted. For example you can remove the bar code, if any, and use a background image with a big red “INVALID” on it.