It seems the current trend is to make a messenger bags that convert to camera bags with the help of an insert. Both Timbuk2 and Tenba offer bags that do this, and a new company is seeking funding over Kickstarter for a similar plan. The UNDFIND One Bag and Waist Shooter are a pair of modular bags, each able to be converted into a different function.
The One Bag pulls double duty as a laptop bag, but with the addition of an insert can hold three like bodies or lenses, and has a number of extra pockets throughout. The Waist Shooter holds two objects, and can either be worn looped through a belt, or over the shoulder. Both have modular and replaceable covers, so you can tweak how they look to your personal preference.
With a month or so left on the Kickstarter project, UNDFIND is more than half-way through the funding, so shouldn't have too much trouble hitting their goal. The benefit for handing over money now is a 40% reduction in price, netting you the Waist Shooter for $39, the One Bag with camera insert for $79, or both for $109. You can see pretty detailed rundown of the bags in the video below, though the way they treat those lenses is abysmal. Come on folks, stashing your glass without a rear cover is just asking for trouble.