I usually try to walk seven laps around my building every day at work during a mid-day break. An employee health staff member put a sign up months ago announcing that seven laps equaled one mile.
Usually, without fail, my cell phone rings or my laboratory beeper goes off or I run into staff or patients and I have to briefly stop.
After the interruption, I would often lose track of what lap I was on.
Finally, I decided on a plan.
I start with 7 pennies in my hand and put one in my pocket after each completed lap.
Odd, yes, but it works just fine for me.
It's cheaper than buying a lap counter and it lets me do something constructive with a denomination of money that is otherwise so hard to use.