I pretty much know what gear I'm in when I run out!

I'm always (mostly?!) aware of what chain ring I'm in, BUT...I must be a freak or something because I cannot see the rear cogs to save my life when I'm on the bike. I've even tried on the trainer where it was relatively safe to lean and contort to try to see 'em. I think it would be so cool to be able to glance back and see what gear I'm in.