Can I get a phonegap application running on iOS 4 to have a background service when it\'s not the active app (e.g. check a url every hour and alert the user if there have be
The best way to achieve this would be to create a plugin for PhoneGap, which runs natively on the phone. PhoneGap recommends that any heavy lifting be done by native code.
Check out the IOS documentation for background tasks, it should tell you what is allowed, and what is not.
http://developer.apple.com/library/ios/#DOCUMENTATION/iPhone/Conceptual/iPhoneOSProgrammingGuide/BackgroundExecution/BackgroundExecution.html