SSD - bikes still have physical reserve taps... at least, mine do! Good idea, although how well they would function on an aeroplane where a spluttering fuel-starved engine could cause more than a bit of embarressment at the traffic lights?!
A thought on some of the comments above about how the operator liked their aircraft returned and what equipment the operator provided - not wanting to sound pompous, but who gives a monkey's?
If you are not happy with the state of the aircraft before flight (eg. you've been pressured into going with less fuel than you'd like or haven't been able to verify fuel levels to your satisfaction), don't take the aircraft at all, surely?
Yes, this is a textbook utopia and yes, we all succumb to outside influences in the real world, but surely it's a fear for your own life that should stop you taking off in an aeroplane you are not happy with or sure of the condition of?
Hersh