LoJack is a stolen vehicle recovery and IoT connected car system that utilizes GPS and cellular technology to locate users' vehicles, view trip history, see battery levels, track speeding, and maintain vehicle health via a native app. Prior to selling a vehicle, LoJack dealers can use the system to manage and locate inventory, view and manage battery health, and recover stolen inventory.

Previous generation of the system utilized radio tracking signal. The system used a hidden mounted transceiver and a tracking computer installed in police cars and aircraft.

The original LoJack system was created and patented in 1979 by William Reagan, a former Medfield, Massachusetts police commissioner, who went on to establish LoJack Corporation in Medfield. Reagan served as the company's first CEO and Chairman. The name "LoJack" was coined to be the "antithesis of hijack", wherein "hijack" refers to the theft of a vehicle through force.

The original LoJack was a hardware and radio based system designed to prevent theft of a vehicle and aid in the vehicle's recovery by transmitting vehicle location to the LoJack receiver.

It was installed in the vehicle and connected to the starting mechanism such that only the original key would start the vehicle. It could also include the incorporation of a scheme whereby an additional step was required to activate the ignition. Prior to starting, it would require the activation of any number of the usual vehicle features such as the radio, headlight switch, or other switched device. Without knowledge of the proper procedure, it would be almost impossible to activate the ignition.

The core of the legacy LoJack system is a small, silent radio transceiver that is discreetly installed in a vehicle. The vehicle is not marked as possessing a LoJack transceiver, and the location of the transceiver within the vehicle varies from one car to the next. Once installed, the unit and the vehicle's VIN are registered in a database that interfaces with the National Crime Information Center (NCIC) system used by federal, state and local law enforcement agencies throughout the United States. In the event of a theft, a customer reports the incident to the police, who make a routine entry into the state police crime computer, including the stolen vehicle's VIN. This theft report is automatically processed by LoJack network computers, triggering a remote command to the specific LoJack unit in the stolen vehicle.

The command activates the LoJack unit to start sending out signals to LoJack police tracking computers on board some police cars. Every police car so-equipped within a 3-5 mile radius of the signal source will be alerted. The tracking units will display an alphanumeric reply code and an indication of the approximate direction and distance to the stolen vehicle. Based on the reply code, the police can obtain a physical description of the vehicle, including make (brand), model, color, VIN and license plate number. Police aircraft can also be equipped with tracking computers; airborne units can receive the (line-of-sight) signals from further away than ground-based units. The signal is received in equipped police vehicles, utilizing a phased array antenna system, hence the four distinctive antennas on the roof. This provides the directional location tracking capabilities of the system.

In addition to automobile theft recovery, LoJack systems are used to recover stolen construction equipment and motorcycles.

In 1998, the company began offering its tracking system to the heavy machinery and construction industry, including entering into an agreement with Caterpillar.[importance?]

By 2013, the LoJack system was reportedly operating in 28 states and the District of Columbia and in more than 30 countries. The company reported that more than 1,800 U.S. law enforcement agencies had LoJack tracking computers in their police vehicles. In November 2013, the company announced they were expanding tracking capabilities to parents, auto makers and insurance companies.

In March 2016, the company was acquired for $134 million by CalAmp, an Irvine, California-based provider of Internet of things (IoT) software applications, cloud services, data intelligence and telematics products and services.

LoJack transmits on a radio (RF) carrier frequency of 173.075 MHz. Vehicles with the system installed send a 200 millisecond (ms) chirp every fifteen seconds on this frequency. When being tracked after reported stolen, the devices send out a 200 ms signal once per second. The radio frequency transmitted by LoJack is near the VHF spectrum used in North America by digital television channel 7, although there is said to be minimal interference due to the low power of radiation, brief chirp duration, and long interval between chirps.

Modern transponder key based systems made the original LoJack starting system obsolete. The system marketed under the LoJack brand since 2021 is a cell phone/GPS based stolen vehicle tracking and recovery system. When a vehicle is stolen, the device transmits data to the LoJack base and includes speed, location, and other data to aid in the vehicle's recovery. Such information is also simultaneously sent to the vehicle owner's computer or cell phone.

In March 2021, the vehicle intelligence company Spireon announced it had acquired the LoJack U.S. Stolen Vehicle Recovery business from CalAmp, joining LoJack users with "nearly 4 million active subscribers from over 20,000 current Spireon customers". CalAmp would still retain and continue to expand LoJack International, which operates as a subscription-based SaaS business, while also retaining ownership of the LoJack patents and trademarks. Under Spireon, LoJack technology moved from RF-based location to GPS and cellular-based technology, growing availability of the solution throughout the U.S. and Hawaii and expanding the solution from only stolen vehicle recovery into connected car technology for both dealers and consumers.[incomprehensible]

In 2023, a group of security researchers announced discovery of multiple software bugs affecting vehicles from nearly all major car brands, potentially enabling hackers to take full control of the affected cars. The most serious vulnerabilities were found in Spireon's fleet management software, which spans 15 million connected vehicles, and could have allowed remote control over a wide range of fleet vehicles, including those used by law enforcement. All identified bugs have since been fixed.