There's a third alert, though it has nothing to do with the sleep-monitoring functions.

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Two people in different parts of the world go to sleep wearing a EEG device like the Zeo, a sleep-monitoring gadget that wraps around the head.

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Each child was given an actigraph, a tiny wristwatch-sized device which allowed continuous monitoring without interfering with sleep.

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Psychologist Chris Dzikowski, the centre's director, said after monitoring Morris's sleep patterns in the laboratory, he found the features displayed were consistent with sleepwalking.

BBC: Simon Morris

Smaller, less invasive, sensors could be especially useful for monitoring premature babies or for studying patients with sleep apnoea without them wearing wires through the night, researchers say.

BBC: Health