OK, I gave them grief for the aromatherapy, but maybe hippychick's onto something.
The Hipseat is basically a fannypack your kid can perch on. By extending this little shelf from your waist, you're able to hold a kid without thrusting your hip out and torquing your spine. More comfortable that way, apparently.
The Hipseat comes in an array of normal colors, and there's an extender, like on the airplane, if you need it. It's £34.95 at hippychick.com.