You'll soon be able to earn Microsoft Points via your in-game Xbox 360 Achievements, judging by a tease from the platform holder.
"Coming Fall: a new way to earn Rewards based on your Achievements!"
No further detail was offered, though a full reveal is promised soon.
For the uninitiated, Xbox Live Rewards is a subscriber-only service that lets you earn Microsoft Points through various promotions. You can sign up over on Xbox.com.