http://www.originpc.com/gaming/laptops/eon13-s/specifications.aspx?tab=specs&active=true&systemid=33
Of course it isn't as thin as the MacBook Air since the MacBook Air was designed to appeal to mainstream consumers and not gamers or anyone else who expects great performance.
Razer makes a 14" laptop that's about the thickness of a rMBP and has a 675GT in it, or something along those lines. When not gaming, it also gets great battery life, but I was purposely avoiding gaming machines as that's not Apple's niche.