In the fight against crime, police are constantly on the lookout for new gadgets and weaponry that can give them the edge. Here are a few of the more intriguing, cutting-edge gadgets that some police departments are using or considering:

Mosquito Sonic Teenager Deterrent: Built with the knowledge that as people reach the age of 20, their inner ear begins to deteriorate, the Mosquito Sonic Teenager Deterrent emits a high-frequency sound that can be heard only by those younger than 25. The noise is designed to irritate -- but not harm -- the ears of adolescents in order to deter loitering and graffiti. (Granted, there are plenty of people over 25 who do both.)

StarChase GPS Launcher: The StarChase GPS Launcher is designed to cut down on high-speed chases by allowing police officers to shoot a sticky GPS tracker onto a fleeing vehicle, letting them back off to a safer distance while still knowing the suspect's precise location. The system is comprised of a miniature GPS receiver, a radio transmitter and power supply encased in a tracking projectile and a launcher that can be either hand-held or mounted on a police vehicle.

Automated license plate recognition cameras: Automatic License Plate Recognition (ALPR) cameras mounted on police cars (and even some helicopters) automatically take photos of the license plates and check them against a database of stolen vehicles, vehicles involved in Amber Alerts and drivers with warrants. When a match is found, alarms go off, alerting the office. With a scan taking only about 20 milliseconds, it's estimated that an officer can run 5,000 plates in a work day, even if the suspect vehicle is moving at 180 miles per hour faster than the cop car.

ShotSpotter Gunshot Location System: ShotSpotter is an acoustic surveillance product designed to detect gunshots and locate their source. A network of sensors containing microphones are positioned around a neighborhood -- on rooftops, utility poles, etc. -- and pick up gunshot sounds. The sensors use GPS trackers and thermometers (Air temperature determines the speed of sound, which aids in calculating a shot's location.) to pinpoint the source of the gunshot. A central server calculates the origin and relays the information to the laptops of police on duty.

Rumbler Intersection Clearing System: In a world in which drivers are so cocooned in their vehicles that they often don't hear police sirens soon enough to get out of the way, the Rumbler adapts the concept of the "booming system" car stereo by utilizing two 8-inch woofers and an amplifier to blast a low-frequency sound designed to make drivers feel the siren. The sound can be felt up to 70 yards away and is aligned with the police siren's modulation so that listeners quickly realize that the vibrations they're feeling belong to the cops and not to a rabid LL Cool J fan.

SmartWater Property Marking System: SmartWater designs products to deter theft, link suspects to crime scenes and recover stolen merchandise. The clear liquid products, each branded with a unique DNA-like code, are sprayed on property to mark it as belonging to a particular owner, aiding in its retrieval after being stolen. Also, SmartWater systems can be set up to spray liquid on a burglar who breaks into a building, marking that person as the culprit. Police then use ultraviolet  lamps to locate the forensic evidence on suspects or on merchandise, providing extremely accurate evidence in criminal cases.

Magicomm Digital Pen: The Magicomm digital pen utilizes a tiny camera, along with image-recognition technology and a transmitter, to capture everything a police officer writes. The information -- for instance, the description of a suspect or a crime scene -- is automatically transmitted and stored in a central police computer.

Project54 Voice-Command System: The Project54 software, installed on a police laptop computer or PDA, allows officers to control a wide range of devices -- lights, sirens, GPS tracking systems, license plate detectors, speed guns -- through simple voice commands that free them up to pursue the suspect without taking their eyes off the road.

Urban Unmanned Aerial Vehicle (UAV): Urban Unmanned Aerial Vehicles (UAVs) are miniature airplanes or helicopters (about five feet long) fitted with video cameras that stream surveillance data to terminals in police cars. The unmanned vehicles, which can circle autonomously for 45 minutes at about 30 miles per hour, serve as an inexpensive option to police helicopters during incidents like pursuits and missing-persons searches.

OnStar Stolen Vehicle Slowdown: General Motors' OnStar in-vehicle safety and security system offers a feature called Stolen Vehicle Slowdown. If requested by police, an OnStar operator can send a signal to a stolen vehicle that is being involved in a police pursuit, restricting its fuel and slowing it to 3 to 5 miles per hour.

Dirty bomb detectors: In the wake of the September 11 attacks, the use of mobile radiation detectors has increased in police departments on the lookout for terrorist activity. These detectors can be mounted on cars or bicycles to alert officers to evidence of a "dirty bomb," an explosive designed to contaminate areas with radioactive dust and debris. Other versions can be worn on police officers like a backpack, while others can be flown in the sky like a blimp in order to provide aerial detection.