With the new Covert model, Timbuk2 expands on their classic three-panel messenger design with a few interesting twists. Namely, the fabric appears normal in daylight but it's specially engineered to be amazingly reflective in the dark, making wearers perfectly visible and, curiously, not very covert. (Click image to see the fabric in detail.)
With a modified design, the San Francisco-based company appeals to bike messengers, as well as to the average Joe who just wants to carry a bunch of stuff around. The Covert satisfies both groups by retaining the extra-heavy-duty stitching, waterproof lining and abundant organization space of their other bags, while adding a couple safety features specifically for cyclists and other creatures of the night. In addition the the glow-in-the-dark material, the exterior features an attachment loop for a safety flasher.
Though it's not clear on their site (another model called Covert only has a center panel of the material), you can pick it up starting at $110 from Timbuk2.