iOS 4: iPod Touch Can Stay Connected To WiFi When Asleep So You Can Receive VoIP Calls And Notification

On the iOS 4 for iPod Touch page, Apple notes that Wi-Fi connectivity will persists even when the iPod Touch is asleep so we can receive incoming VoIP calls and notifications from compatible third-party apps.

There is no word if this feature will also be available for iPhone users, but it will probably not, because ( usually ) cellular data is pretty persistent. But, users would definitely welcome this feature on iOS devices.