A remote car starter is essentially a small radio transmitter, usually attached to a key fob, that connects with a radio receiver attached to the starter mechanism inside the car. When the transmitter is activated, the receiver automatically starts the car without the driver having to be present in the car already.
Remote car starters are particularly useful for drivers in very cold climates, as they can use their remote car starters to let their cars' engines warm up and get the heater and defroster going without having to trudge through snow or wait outside in subfreezing temperatures. Remote car starters can also be used to start up air conditioning before getting inside a car in an extremely hot climate. Remote car starters cannot generally be used with cars that have carburetors, however. Typically, remote car starters flash the car's lights to let the drivers know that the system is working.
Some high-end remote car starters come with add-on features, such as a car locator, interior light activation, driver paging, keyless entry, proximity unlock and fast engine warm-up. In addition, some are pre-programmed with an array of security features including an alarm system, a panic siren, a starter disconnect switch and anti-hijack features.