You would be surprised at the number of places you can find a GSM SIM card. Outside of your mobile phone, they can be found in power meters, water meters, vending machines, etc. These SIM cards (virtually identical to the one in your mobile phone) are used for machine-to-machine communication. Essentially all of these devices need to make mobile phone calls to other machines, usually for billing.
Machine-to-Machine Fraud/Theft of Service
Because it’s just machines talking to other machines, they don’t really need a voice plan and most if not all of their usage will be data.[...]
Cars with Smartphones: Telematics, Diagnostics, and Attackers
Power meters aren’t the only devices that need their own smartphones. TV commercials by auto manufacturers show a man calling his wife, before her airplane takes off, to ask her to remotely unlock the doors of their car. Remote unlocking, engine starting, GPS/mapping, vehicle recovery, and crash assistance are features of what are known as telematics systems. Usually you would pay a monthly fee to the manufacturer to have access to all these features. In some cases you can get diagnostic output from car sensors emailed to you.
