Maybe something like a Shopify, although those are unsurprisingly starting to spring up left and right. I'm thinking more of something like building a nice, consistent cross-platform API for deals.

Unfortunately, sites like Groupon have draconian developer terms of service (http://www.groupon.com/pages/api-terms-of-use). Basically, what they're saying is that you can show Groupon deals to end-users, but you can't do anything else.