This is a great idea! Without saving money you cannot start anything, the only problem with saving it is slow and requires patience and time to see the reward. Your idea makes it easier to save but still does not increase an immediate gratification. if you can combine it with a small reminder that you are doing good by saving; it may increase the value and stimulate future saving. it should not be monetary reward. It might be a text message saying how good you are, or a matching donation, say 1% of your saving, from a bank to a charity of your choice, or anything else that tell that you have done good.