I know that @jerrybanfield is hiring a developer and paying him from @budgets to develop a peer to peer transaction system, so that if I have $500 and you have 150 SBD, we can exchange them on this system.
Not exactly what you'd like but definitely a step in the right direction! I have a few developer friends coming to the platform soon, I may mention it to them.
Isn't that what Blocktrades is already?