Actigraphy
A method of estimating sleep by recording movement for days with a small device worn on the wrist.
A little more detail
A movement sensor worn on the wrist records for days or weeks; algorithms classify still periods as sleep and active periods as wake. The AASM 2018 guideline conditionally recommends actigraphy for assessing insomnia and circadian rhythm sleep wake disorders, for monitoring total sleep time before an MSLT, and for estimating total sleep time when added to a home sleep apnea test. It strongly recommends that it not be used in place of electromyography for diagnosing periodic limb movement disorder.
Source: Smith MT, McCrae CS, Cheung J et al. Use of actigraphy for the evaluation of sleep disorders and circadian rhythm sleep-wake disorders: an American Academy of Sleep Medicine clinical practice guideline. J Clin Sleep Med. 2018;14(7):1231-1237. doi:10.5664/jcsm.7230