Everything else happens at the iOS system level: you pair the Pebble and select “show notifications,” and you’re theoretically off to the races.
Interesting description of an iOS feature I didn’t know about: your iPhone can forward notifications from any app to a paired Bluetooth device — if you read the full review, it becomes clear that this functionality is still in its infancy, but I wasn’t aware iOS could do it at all and had assumed Pebble’s own app would have to facilitate a lot of their functionality.