Hey, let's start one. And maybe we can offer to sell it to google for $6 billion.
Seriously, there are similar concepts floating around, but I haven't found any of them to be worth my time. You'd generally need a deeper discount that what they typically offer.
FWIW, I did buy a groupon for the SPG La Paloma in Tucson this week. $75 in room credit for $25 (and I didn't really have to pay the $25 -- I had a $10 referral bonus). So worth looking around for these.