The long awaited for push notification service for the iPhone is available in iPhone OS 3.0 and developers are being encouraged to start testing push with Apple's server. Push services have the potential of bringing a whole new level of innovation to iPhone app development. However, the potential cost involved in developing and maintaining a push server for your app may be prohibitive. Yes, Apples does maintain and provide access to the Push Notification Service, but you, the developer, must provide the "3rd Party Server" as shown in the picture above. Apple only provides the piece that allows a well formed message to be sent to a designated (and registered) device. You have to form that message and designate the receiver. And for that you'll need your own server. Erica Sadun put it this way in a recent article at Ars Technica:
Consider an application with just 10,000 users. It might service a million uses per day, assuming update checks every 15 minutes. More time-critical uses might demand checks every few minutes or even several times a minute. As the computational burden builds, so do the hosting costs. While cloud computing provides an excellent match to these kinds of needs, that kind of solution comes with a real price in development, maintenance, and day-to-day operations.She makes it sound fairly daunting and this may scare off some developers. But I think developers will find a way to make this work either by using cloud computing or sharing resources. There's one company, macminicolo.net, that's already offered to host push services for developers. They advertise their service starting at $35 per month. And if you are staying current with the iPhone Developer Forums, you'll see that code for these back end push servers is already being shared and is running on Mac and Linux servers. I think it would be worthwhile to take some of this work and put it on the cloud using Amazon's EC2. The initial costs of running a low-end Amazon Machine Instance is around $72 per month (doesn't include data storage or network usage). Between that and the results of the experiment macminicolo.net is conducting, we may find that the costs can be contained.