I'd be very interested into this feature too. Most of my purchases these days happen thorugh Steams "an item on your wishlist is on sale", since the easy access to digital games has me swamped in hundreds of games, I want to play and never will have the time to.
Having a wishlist, and something that reminds me of items on it, is a major driver of purchase for me.
Note that the effect isn't about having discounts; It is about having an easily managed list, that gives me occassional reminders. On Steam, the latter simply coincides with sales.