Category 1: sleep tracking
Phone and wearable trackers infer sleep from movement, sound and heart rate. They are reasonably good at total sleep time in aggregate and poor at sleep stages — quiet wakefulness is routinely scored as light sleep.
The risk is behavioural rather than technical. For some people, checking the score creates a feedback loop: bad number, anxiety, worse sleep, worse number. This has a name — orthosomnia — and the treatment is to stop looking.
Verdict: useful for awareness, harmful for the anxious. If you score yourself every morning and feel worse when the number is bad, take a two-week break.
Category 2: relaxation and audio content
Guided body scans, yoga nidra, bedtime stories, soundscapes, breathing timers. These are simply delivery mechanisms for techniques that work — nothing about the app is doing the work.
Verdict: fine, and useful if narration helps you stay with a practice. Choose based on whether the voice and format suit you, and ignore any claims about proprietary sound technology.
Category 3: digital CBT-I
Structured programmes that deliver CBT-I: sleep diaries, personalised sleep windows, stimulus control instructions, and cognitive restructuring exercises, sometimes with a coach. Randomised trials support their effectiveness, and they solve the main practical problem with CBT-I, which is access to trained providers.
Verdict: the only category with real evidence, and worth considering if you cannot access a trained practitioner.
How to choose
- If you have chronic insomnia — three or more nights a week for three months — look for a programme built on CBT-I, not a general wellness app.
- If you want help winding down — an audio library is fine; pick one you will actually use.
- If you are curious about your sleep — track for two weeks, then stop. Do not build a habit around the score.
Warning signs
- Claims to "hack" or "optimise" sleep stages with sound frequencies.
- A sleep score presented as more precise than it can be.
- No mention of stimulus control, sleep restriction, or cognitive work in a product claiming to treat insomnia.
- A subscription model that depends on your continuing to check daily.
The cheapest effective option
Everything an app does, you can do with a piece of paper. A sleep diary plus consistent stimulus control and sleep restriction beats most products. And if your problem is a body that will not settle, no app replaces ten minutes of slow movement.