Here's an article from Media Daily News.
It seems that after remaining very quiet about the Portable People Meter, a project they are supposedly working with Arbitron on developing, they have now very publicly put it on their R&D front burner. Why? Because after about three years (maybe longer) of saying that they were hoping to work cooperatively with Nielsen on the project--which, if you don't know, will use inaudible tones embedded in all sorts of media from radio to tv to cable to in-store music--have now started discussing a "Radio First" strategy. This is, supposedly, where Arbitron will utilize the PPM technology and get the radio industry measured using it first.