Last year, Google announced a points-based reward system for the Play Store, but it was limited to Japan. That same program now includes South Korea. In case you've forgotten, the Play Store Points system rewards you for shopping and spending money.
For South Korea, the conversion rate is 1 point per ₩1,000 spent for the base level. Once you move up to Silver, it becomes 1.1 points per ₩1,000, or 6 points for ₩5,000. There are special ways to earn more points, and Silver members and up are eligible for weekly rewards.
It sounds like a neat system, one that I can see doing well in the West.