How do I make a circuit that will flash and beep faster and faster?

To elaborate, I want to make a prop for a convention that looks and acts like a pipe bomb from Left 4 Dead. I was planning on making it out a piece of ~1-2 inch diameter PVC pipe about 6 or 8 inches long. The key is to be able to turn it on, have it beep and flash, and then throw it and have it beep and flash faster and faster until it either just turns off or, even better, makes an explosion sound. It need only run for 10 or 15 seconds at most. The prop in the game has external wiring and whatnot, but I can always add that cosmetically later. Thnaks for any tips.