I dont think Tasker and IFTTT have anything to do with each other.
IFTTT is a web based service that responds to an internet based event.
If This Then That.
So it could be If then
or If then
There are a list of events and a list of actions.
Where this is useful for Pebble is that they will be creating a pebble action channel so you could have If then
This notification is generated on the IFTTT server and sent to your pebble via your phone. It doesnt respond to events on your phone directly. There wouldnt be any point. Your phone would have to send the event to IFTTT (if thats even possible) and up to 15 minutes later you'd get the notification on your watch. Why not send the notification straight from your phone to your watch.