Two of these are readily available kits, one of them was used in a popular TV series just last month, while the third example is a home made spin using an off the shelf Arduino UNO. a 20x4 Parallel LCD & a few LEDs. We also added a Real Time Clock for good measure.
Step 1: The Bomb Prop
Designed by Nootropic Design (http://nootropicdesign.com/defusableclock/) , this excellent Arduino compatible Defusable Clock looks so much like a Hollywood Bomb, that it was featured last month in an episode of CW' The Tomorrow People. You can order your kit straight from Nootropic Design like I did or get it from the Maker Shed as they are now carrying it also.
At $33, it's not that expensive as the Arduino is built-in. The kit includes all electronics, but only electronics. I made 2 Dynamite looking sticks by soldering then wrapping 3 C Batteries in each laser printed grocery bag and made the other 5 Dynamite sticks by cutting my wife's broom in sections that were the same total length as the 3 batteries combined.
I cut grocery paper bags in 8 x10 sections & fed them to the laser printer to print "Dynanite" in red for additional effect.