As a cager, I find that obnoxious Fredly bright neon yellow jackets do wonders for visibility. I've seen riders way off down the road because of their large spot of yellow jacket than from their red rear blinky. Combine that with a blinking light.

I think flashing modes generally will run for 2x longer than steady modes. The light should tell you the run times. I would recommend a floody light for visibility. XM-L or P7 flashlight will do. shiningbeam.com has some nice lights, but none of them seem to have flashing modes. What battery or form factor are you interested in? The KD C8 is a popular inexpensive decent light that has strobe mode. And it's perfect for night use. The Magicshines also have strobe mode. There are lots of MS and MS clones out there. You could purchase an older P7 version pretty cheap.