Hubert - If you are looking to reward your customers after check out( on a random basis) , Neowauk Events App can do that.
On the diamondcandles, looks like they hand out a number and later customers come back to see if they won anything..
With Neowauk Events, that wont be possible, but after order completion, customer can be allowed to win instant offers, based on the rules you define.( In other words this is an instant sweepstake, where your customers will get to see the result instantly)
Let me know if you have questions
