dev it (I'd think) into a monthly fee site that updates the current gold rates (for the fee members, send them text messages per their requirements (when it grows 2 points, 3 points..etc) per their needs). then, once you have a good amount of members, sell
Gold +monitor is not a good keyword combo unless you are targetting a specific market. So Unless you a theme in mind this is probably regfee or lower. http://www.sitefirms.com/domain-sales/monitor