Apps that are meant to improve sleep are likely to make problems worse, experts have warned.
Researchers said they reveal little about sleep quality, lack accuracy and create stress.
There is also a risk of people becoming obsessed with default targets, such as getting eight hours a night, they said.
Dr Guy Leschziner, who runs a sleep clinic at Guy’s Hospital in London, pointed out people need different amounts of sleep.
In addition, monitors in labs use hundreds of electrodes and cameras but home devices rely only on movement.
He told Cheltenham Science Festival: “People have developed significant insomnia as a result of sleep trackers or reading things about sleep deprivation. That obsessional state about sleep makes sleep even more difficult.”