Ignition interlock devices are in-vehicle mechanisms with a tube into which drivers must blow to show a low or near-zero blood-alcohol concentration before the car will start. These devices are usually required for repeat offenders as part of their sentence or in order to end a license suspension. Passive alcohol sensors measure breath alcohol by means of electrochemical fuel cell technology. Sensors can be placed in a flashlight and used by police officers to detect the presence of alcohol and help establish reasonable suspicion for further sobriety testing. This can increase efficiency in detecting drunk drivers at checkpoints. Continuous transdermal alcohol monitoring detects alcohol consumption by measuring ethanol, a byproduct of alcohol consumption, in skin perspiration. The monitor locks to the ankle of an offender and information is uploaded to a remote server. New technologies are being developed that could be installed in every vehicle. Among them is an alcohol detection device that uses transdermal technology located on the steering wheel. Before a vehicle so equipped will start, the driver's blood-alcohol level must be below a preset limit. Another technology being developed is touch-based alcohol testing that uses optical technology that could require both biometric identification of the driver and his/her alcohol level on a touch pad before a car will start.