Do you need to pay for a subscription to enable your iPhone app to receive push notifications?
I’m looking to create an app that allows the client to push notifications to all users who have downloaded that app. For this to work, do you need to pay for a subscription to a push notification server or something like that?
You will have to create your own server to communicate with Apple servers. You can also use Urban Airship and communicate with them via their API: http://urbanairship.com.
More info here: http://developer.apple.com/library/mac/#documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/ApplePushService/ApplePushService.html