Some years back a new flow meter appeared that pumped fluid round a U-shaped tube. The tube was arranged to vibrate in a plane perpendicular to its U plane, and the gyroscopic couple of the fluid flowing round the circular bit by precession caused the tube to twist around its axis in the U plane. This could be picked up in some way I can't recall, but the magnitude of the vibration depended on the total angular momentum of the fluid flow round the bend. This gave a very accurate measure of mass flow, and could presumably be used in petrol pumps.
I'm not sure if it is quite so accurate, but at least one make of water meter now has no moving parts at all but measures flow velocity using ultrasonic doppler shift. At least it's accurate enough for them to base your water bills on the measurement!