While listening to the latest Bombcast (6/8/2010), the Sega Activator was mentioned in a conversation about PowerGig: Rise of the SixString (started at 45:04), specifically the AirStrike Drum controller.

I found this promo video for the Activator on YouTube (and also GameTrailers) and at 2:35, the phrase "You are the controller" surfaced and totally reminded me of Natal! I suppose it didn't actually function very well - it placed 3rd on an IGN list of worst game controllers - but I guess a minor plus would've been the compatibility with most Genesis games? (Oh, man - that dude's hair is so 90's!)

Here's someone trying the Activator with Mortal Kombat II and getting frustrated at not able to do combos. [YouTube]

The Activator being demoed at WCES '93 in Las Vegas with another fighting game, Streets of Rage 2. [YouTube]

Finally, the inventor (Assaf Gurner) plays Tocatta & Fugue in D Minor using the peripheral, also known as the Light Harp. [YouTube]