There's a "movement" out there called strobism, and someone came up with an idea. I'll link to it below. The general idea is to add a calculator to the camera that uses the current whitebalance to calculate which gel should be used on an external flash. Especially the G9 (amongst others) is a camera that really could use this feature.
BTW Apologies if this has been posted before. I searched for "strobist" and "white balance calculator"