I know of a certified WiFi device, was rather new in 2010. They apparently had to block parts of the frequency spectrum normally used though. Rather peculiar if others have been using it without restriction since 2009... got more info on that one?
Just to clarify, I meant Boingo has provided WiFi for Internet Access from PAX devices since 2009. Not sure if anyone is using WiFi in-seat entertainment devices yet but sure sounds like a good idea.
This article covers some bits of the certificaion process:
Clearing WiFi To Fly: Aviation Week Article