WestJet has had one for years. I hadn't even bothered signing up because unless you purchase at least $1,500 in 12 months then you don't earn a dime. These policies were changed a couple days ago so hopefully I can start earning something on my frequent YYZ
As for Air Asia X, good for them. Are these points transparent between Air Asia subsidiaries and Air Asia X? There was a time a few months ago when I was flying Air Asia Thailand just about every three days, this program would have been helpful!