If you're walking down the street this week and hear a cop car coming, you might just feel it, too. That's "the Rumbler." Some 25 police cars have already been fitted with the device, which gives off a low-frequency sound wave producing vibrations that can be felt 200 feet away. The idea is to give pedestrians and hearing-impaired (or volume-enhanced) drivers another way to figure out that cop cars will run them over if they don't move. About 100 more rumblers will be installed tomorrow as police spend the next week making jokes about the vibrators in their cars. [NY1]