But it isn't coming - the current Nectar app even has a specific section in it explaining they have no intention of introducing a barcode to be scanned within the app itself as their main retailers' barcode scanners aren't capable of reading it from the iPhone screen.
Given that there's not much chance of implementing Passbook functionality.
Really? That's poor. They could at least use it to push coupons to the lock screen
edit: they just enabled this in an update