this bike computer is less than 20 bucks and it can count magnetic pulses per hour. so you would have "live" fuel volume per hr.
http://www.cateye.com/sites/cateye/u...s/en/VL500.pdf
so i borrowed the little woman's speedometer off her bike and placed it next to an operating fuel pump, and the display says i going 175 km/hr.
on the bike there is a lower limit on speed, below which, the display goes to zero. this occurs at 2 Hz more testing is needed to determine if the pump will trigger the counter at vary low volumes. or what the flow rate is at 2 Hz. i am thinking make the volume of the pipe after the pump very non-compressible so that the accumulated pressure drops rapidly, there by
causing the pump to cycle on and off (short cycle) for a small volume of fuel.
this bike computer has better spec's, if they are true. $22 (topeak 130)
http://www.topeak.com/sub/documents/M-TPC3-GB-5-05.pdf