[underwater]

The creators countered by saying those reviewers were testing on uncalibrated phones. The app normalizes the movements so even if it detects only very small movements it will still render a graph with full range of movement.

I don't know if this is true but I saw in their changelog http://mdlabs.se/sleepcycle/changelog-v3.0.html that they "removed "dreaming" from graph legend we've done a lot of research around this with help from sleep scientists and determined that Sleep Cycle cannot reliably detect when you are in REM sleep".

That makes me think they're legit. Their test function is also pretty convincing. It detects large and small movements quite accurately.

[tudorachim]

If they can't detect when you're not in REM sleep and wake you up at that point, what's the point of the device?

[nater]

As I understand it, grogginess is associated with waking from deep sleep (no movement), not REM sleep.