I have Bar End shifters, so I can't answer the Shimano/Campy thing... but a quick glance down and back between your legs is pretty easy.

I've been staying out of my smallest gear recently and find this easy to do even while climbing to see how many gears I have left before the smallest.

V.

PS Lisa with bar ends - straight up for the rear is the easy gears, the middle is the middle gears, straight down is the hard gear. Yes there is some variance in there, but this line of thinking works for me. And it doesn't need to be exact, you just need to glance to keep from cross chaining.