WP Curve reminds me of Elto (formerly Tweaky), except it's based on monthly fees versus one-off pricing. Dan Norris and Alex McClafferty started WP Curve recently, and Dan notes in this great interview with Brian Casel that WP Curve is up to thirty monthly customers. I loved this interview because it really highlights the challenges of creating a business with sustainable income, and tells the real story of starting off.
WP Curve seems like an interesting service with potential to cater to a hard to monetize niche: recurring support. There are definitely people in this space. Two of my favorites are The WP Valet and WP Site Care. But all of these companies seem to be taking slightly different angles on supporting websites. I'll have to analyze it in more detail soon.