TABLE 3. Selection of Devices That Have Been Used to Acquire PPG Signals Continuously From Ambulatory Subjects. Definitions: GSR—Galvanic Skin Response; Temp—Temperature; Accel—Accelerometry; and BT—Bluetooth.

Device	Ref	Other Signals	Site	Data capture
Biostrap Biometric Set	[304]	two PPGs, accel, SpO2	Wrist	BT, storage
Biovotion Everion	[305]	accel, GSR, SpO2	Arm	BT
Cossinus° One / Two	[306]	accel, temp, SpO2	Ear	BT
Empatica E4 Wristband	[307]	GSR, temp, accel	Wrist	BT, storage
Nonin 3150 WristOx2	[86]	SpO2	Finger	BT
Polar OH1	[65]	accel	Arm (flexible)	BT
PulseOn OHR Tracker	[194]	accel	Wrist	BT, storage
SmartCare pulse oximeter	[72]	two PPGs, SpO2	Finger	BT