The wolffepack is a backpack with a detachable cargo section that can be swung around to the wearer's front as and when required. The brainchild of British engineer David Wolffe, the wolffepack solves the biggest problem with backpacks, which is that you need to take them off to access its contents.
The wolffepack uses the proprietary expetoSYSTEM orbital trapeze technology, which requires the user to pull a magnetically-secured handle on the front of their shoulder strap, causing the cargo pack to detach from the back section of the wolffepack and drop down below it.
Wolffe is currently running a Kickstarter campaign to raise funds for production of the wolffepack. A pledge of $136 will get you set up with a Metro or Escape pack if and when the campaign hits its fundraising goal.