Meanderthals
A definition from the October Playboy:

\me-AN-dur-thols\ n, aimless, slow-walking pedestrians who mindlessly get in everyone else's way on sidewalks, in malls and in crosswalks, often while preoccupied with a cell phone.

Those of the cell phone wandering ilk are also known as "rude assclowns." My favorites, though, are the cellphoners behind the wheel, who respond to a honk from you by giving you the finger and staying exactly where they are, green light or no greenlight...as if to say, "Can't you see I'm on the phone!?"