fuel level detector

What's the best way to measure the level of fuel within a tank?
I have some hazy ideas about using a capacitor, such that as the fuel level changes the distance between the capacitor plates changes as well.
What are your ideas? :?

Consider what's used in existing equipment, basically just a float moving a potentiometer. Assuming it's on a moving vehicle?, you also need to be very aware of the level changing as the fuel splashes about.