I recall professional photographers in my youth packing around belts of batteries to handle their flash units.
Now, the digital photographer can have a belt unit too. This one carries a 20GB drive and a wireless network connection. A card is plugged into your digital camera's CompactFlash slot to communicate wirelessly with the beltpack.
It's not cheap. DiceAmerica charges US2,000 for its Wi-Pics Workflow unit.