This is a great idea. The part could Just be a wheel with the hose wrapped around it. All the kerbal would have to do is pull the hose over to the ship and plug it in.
A flexible hose that a kerbal could pull to refuel craft at bases ect. It could transfer all types of fuel. This would make it a lot easer to refuel ships on planets. Also you could have a power transferring version to recharge ships and rovers.