Windows Mobile 6.0/6.5 - Push Notification

My mobile application needs to ping web service (WCF) periodically to get the latest data from server. The problem is, thi开发者_开发知识库s is done periodically even if there isn't anything new on the server. Is there any way that Server notifies device about the change? Like Push Notification? I have read that Push Notifications can be done by SMS and Email. But, both has disadvantages.

You can try with long lived HTTP requests...

http://msdn.microsoft.com/en-us/library/aa446486.aspx