why not just use your iPhone to control your atv? it has an accelerometer why not use it, without developing a new product.
As someone else said: why buy a "remote" for $500 or $1000+ when you factor in a contract for a device that costs $99?
But also, this whole- "just use our iPhones"- idea that comes up over and over ONLY might make sense if you are single living alone. If Apple were to make the

TV DEPEND on an iPhone as remote, every time you leave the house with the remote, everyone else at home can't use the

TV (unless you buy up to ALL of them a $500-$1000+ "remote" too).
Stationary A/V devices need a
stationary remote (that doesn't cost $500-$1000+). If the remote is also a phone, etc and thus something that begs to be taken out with it's owner every time the owner leaves the house, it's a very BAD remote for anyone beyond those single, living alone. For example, I'm on the 3rd night of a trip right now. My "remote" would have been away from the home & family for 3 nights. Think how happy they will be.
Same with the "airplay" device (only) idea.
Same with the "iPhone as game controller" idea.
Etc. One piece is to be left at home and the other piece goes out every time it's owner goes out. If you are NOT single living alone, take the A/V equip remotes at your home out with you and see how happy the family/roommates are when you bring them back later. Then, you'll get the key flaw in the concept.