The closest I can think of is the Apple TV's "TV App" which will aggregate searches and a lot more too, such as shows you've bookmarked, single sign-in, and "up next". This is SUPER cool, but unfortunately Netflix won't play ball, which really cripples it for me.
For just search, Siri voice search on works quite well on Apple TV and aggregates across services including Netflix.
Amazon Prime is currently completely absent from ATV, but rumored to be coming soon.