The Messaging and Security Feature pack combined with Exchange SP2 gives us mobile users direct-push email. So how does this work, well a blog article by the exchange team gives a detailed insight into how it all works.
Why do we want to know how it works? Well, the same technique can be used in our applications to make them respond immediately as information on the server changes. Typically most mobile applications currently use some form of polling or SMS notification to initiate a sync. This can both be expensive and not particularly effective.
Using the technique described by the exchange team, Alex Yakhnin shows how you too can have an application that is always up to date!