Thanks @OmegaStarScream - CoinSwitch comes close, but you have to specifically select just one exchange manually, so it's not going to give users the kind of multi-exchange instant-best-price settlement possible unless you happen to fluke picking the one exchange that's got the best ask order at the instant your trade is executed (so basically - rare).
It is giving you the best price for each exchanges that happens to show after you put the crypto you're about to exchange and how much you're going to trade for it with the selected coin that you want to receive. And it's not actually instant because it takes for you to receive the coin that you have exchanged because of the confirmation time. If you exchange bitcoin to another crypto, as long as your transaction isn't confirmed yet, you have to wait for it before they exchange it.