Nothing says bomb like a ticking clock.
In this commercial I made my bomb out of a cool old tackle box, a fist full of computer wires, cpu heat sinks, circuit boards, some cable management tubes and of course a big ticking analog alarm clock! I got the clock, and the tackle box at goodwill, the rest I had lying about. Total coast $3
Oh, I used a label maker to make my own "bomco tm" and "C4" labels...
http://www.poptent.net/media/20730
how about making a digitial count down clock in after effects and just playing it back as a movie on the screen. Live will look better then post..
when we talk about after effects, is it making a number at a time and putting them all one after another to make it look continuous?