I saw this type of technology a few years back when some people from georgia tech's mobile group (they have some name i forgot) were showing off the same thing. You call in and start playing tetris with your phone.
The technology behind it is fairly old, aside from the cell phone part. My understanding is that it uses DTMF signaling, which has been around for at least 30 years in normal phones. I guess it's a lot less fun with a land line, unless you happen to live across the street.
