Actigraphy is a simpler alternative to expensive laboratory techniques for measuring how deeply a person is sleeping. It is explained in a paper by Ancoli-Israel et al. (2003) in the journal SLEEP. It involves measuring how still a person is while he or she is sleeping with complete stillness equating to deep sleep. Typically an accelerometer is attached to the wrist of the non-dominant hand and movement over time is recorded and is the basis for a number of consumer sleep monitoring devices (e.g. FitBit, WakeMake) and mobile phone apps (e.g. SleepCycle, Sleep as Android),