Is it possible to replace/delete the existing push notification when its not yet unread?

[akkina9]

Usecase: Message App: When I get a new message, I would get a push notification which says '1 Unread message'. When another message comes (and I did not take any action on previous notification), I would the previous notification to be replaced (or delete and new one) to say '2 Unread messages'.

Any ideas on how I could accomplish this on both iOS and Droid?