We are considering using Azure Notification Hubs to delivery messages to iOS and Android devices. Is it possible to track when a user opens one of the push notifications? Maybe the only option is when "tapping" the notification on the device this causes the the app to call-back to a server?
I understand that there are many commercial SAS solutions that offer this kind of service but I really like the simplicity and low cost of the Azure offering so it would be good to here how people have solved this problem when using Azure Notification Hubs.
This is not a feature that is built in to Notification Services. You will need to write your own code for Android and iOS to detect when the user has tapped the notification, and respond accordingly (such as calling an Azure-based or proprietary Web service that you create explicitly for the purpose of handling this event).
For iOS, this topic might help: Detect if application: didReceiveRemoteNotification: fetchCompletionHandler: was called by tapping on a notification in Notification Center
For Android, this topic might help (not perfect, but close): How to detect if a notification has been dismissed?
Conceptually, this should not be a difficult thing to do. I would definitely roll my own solution along these lines before I considered a commercial solution if this was all I needed.