You're serious about fitness so you wear a fitness tracker and it reminds, nudges, & guilts you into action to make those 10,000 steps.  Some also measure sleep and now the experts say in some cases that can be a bad idea.

The Daily Mail reports that "these trackers rely on data that doesn't truly represent sleep." And for another, using one can actually cause insomnia, as you may begin to "obsess" about sleep."
There is even a name for it. It's called orthosomnia, and it can cause stress and anxiety, which produce hormones which will keep you awake.  It's like when someone says "for the next ten seconds, try not to think about an elephant".  Result -all you CAN think about is an elephant!
The best measure is your own experience say the experts, "If you wake up every day and feel refreshed, are awake throughout the day and are ready to sleep at the same time every night, then you're probably getting enough sleep for you and you don't need an app to tell you that."