You don't even need a smart contract, the CME will be starting to sell cash settled BTC futures in two weeks: http://www.cmegroup.com/media-room/press-releases

You don't even need a smart contract, the CME will be starting to sell cash settled BTC futures in two weeks: http://www.cmegroup.com/media-room/press-releases/2017/10/31/cme_group_announceslaunchofbitcoinfutures.html http://www.cmegroup.com/media-room/press-releases/2017/10/31...