A whelen system will be WAY overkill for what you're looking to do. My friend's dad was on a police force so we got my friend's jeep fully outfitted with all the lights and an arrowbar hooked up to the whelen controller.
You'll want just a basic wigwag/flasher box. However wiring it up might take some trial and error to get it to work right and to still work properly with the hazard button (it took a LOT of time to get it right on my friend's jeep). We hooked it up to the hazard/turn signal lights but couldn't get it to work with the controller, turn signals, and hazards all at the same time (he ended up putting separate strobe bulbs into the turn signal housings). The easiest would probably be either the parking lights or the fog lights.
Check out some websites for different controllers, they should be relatively cheap for just a wigwag (ie $20-50) compared to something like a full whelen system.
04xt/4eat, 16g, STI bits and bobs