This precision monitor wakes you at the first sign of perspiration or drop in skin temperature. DL2032 or CR2032 battery may need to be replaced. The Giant Biosensor Nighttime Cold Sweat Alarm is a device worn on the wrist or ankle that sounds an audible alarm and vibrates to wake those people who experience interrupted sleep due to drenching night sweat moments causing the need to constantly change your sheets & the clothes you sleep in. It triggers an alert upon detecting either a drop in skin temperature or the presence of perspiration which is how the body regulates its temperature. Night sweats may be caused from a variety of factors. Your physician should always be consulted in cases of persistent night sweats. Other than the purchase price, there are no on-going costs to run the monitor other than changing the batteries every six to twelve months. Requires a CR20232 battery (not included) Note: It is normal for your device to sound occasional false alarms. These can be minimized by ensuring the band remains snug during use or wearing on the ankle to keep at a constant temp under blankets.