A quick question for all of you .. .. ..

How do you count mileage when training on a cyclops or similar trainer? My computer functions off my front wheel which is static and therefore doesn't register any mileage or speed. Do you get a second computer and hook it up to the rear wheel, or just take your time on the bike and apply your "average" speed to it in order to get distance?

Thanks, Peter

PS the other real question is how does anyone do more than an hour on a trainer at a time without getting terminally bored!!