Simple question - does the 550 have a tilt sensor?

Mine doesn't light up when I pick it up, but sometimes it will spontaneuosly light up if it is sitting on one end of the couch and I sit down on the other.

What gives?

Thanks.

I've wondered the same thing myself. Mine in my bedroom does the same thing.

It has a tilt sensor, but it only lights up the remote if it's been idle for more than 2 hours. I've no idea why...