Blackberry. Increasingly popular usage for the communication tool as it becomes more ubiquitous.
As you walk out of the barber shop, someone calls out but you say "Gotta run homie but, yo, hit me on the Double B.
The signage that goes with it is: left hand out and imaginary-type on it with the right fingers a number ot times- tap, tap, tap.
Rappers now carry the Blackberry and it's becoming cool to include it in lyrics.