actigraph
noun
ac·ti·graph
| \ ˈak-tə-ˌgraf
\
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Medical Definition of actigraph
: a small device usually worn on the wrist that records the activity level of the body by sensing physical movement and that is used especially to measure the amount and quality of sleep
Researchers measured the sleep time of 2,978 women by equipping them with an actigraph, a watch-size device worn on the wrist that measures periods of activity and inactivity.— Nicholas Bakalar, The New York Times, 16 Sept. 2008 Actigraph data accurately identify periods of sleep and wakefulness and yield estimates of movement, the researchers say.— Bruce Bower, Science News, 20 May 2000
Note: An actigraph consists of an accelerometer and a memory unit and is used to collect data typically for a period of several days to one or two weeks.