Allow message filtering before delivery

Many applications allow sending of messages but are not very granular about different message types.

Example: backup application that sends a message every day for whether the backup is successful or failed. It would be great if only the failure messages get delivered to the device.

If text or regex filters were supported on a per application basis that would be a great way to filter out stuff that doesn't require a notification. And of course filtered messages should still count towards daily allowances.