Full disclosure: I have a Fitbit Surge (the ugly huge watch looking thing that has GPS and a heart rate monitor) and I find it super useful to track my runs/assorted workouts and set goals. It also helps me see that I'm a little overtrained when my heart rate doesn't seem to come down from the 70s all day long (freaky to see when you normally rest in the mid-50s, I was super worried the first time I noticed it).  Having said that, this week I had a fat tell me that he forgot to put on his Fitbit that morning (he has the one that is just a step counter, I think it's called Flex) so he was trying to avoid walking too much since it didn't count anyway. Fitbits are like yoga pants or running tights, just because you're wearing one it doesn't mean you worked out...