sCall refers to a security measure that is offered by ARC Europe Group. In case of vehicle theft, an sCall triggers a stolen vehicle tracking system which helps to locate the vehicle.
Different car companies offer a similar service or additional feature. The general procedure for activating the tracking system is the following. If the vehicle is stolen, the owners need to report it to the police. The police will give them a report number. The owner can then present the number to the car company that, in turn, will locate the stolen vehicle via the tracking system. This information will then be transferred to the police.
It is important to note that while a lot of car companies offer this service, the fees for it differ. For example, Volvo and Ford offer stolen vehicle tracking for free, but some may ask a yearly payment. For more information on different car companies in relation to that topic, see here.