SIM card for GPS tracker - it all comes down to this
M2M Sim Card Annual Renewal - Rewire Security
2G Sim Card for GPS Tracking Device Tracker GSM Car Pet Child Smart Watch Alarm | eBay
What about GPS trackers without a SIM card?
GL300MG Portable Personal 4G Real Time Mini GPS Tracker for Vehicles, Cars, Kids - SIM Card Included with Mini Magnetic Weatherproof Case: Amazon.co.uk: Electronics & Photo
What To Look For When Buying a GPS Tracker - FAQ
SIM Cards for Trackers - Free • Personal GPS Trackers
O2 02 Sim Card Pay As You Go for 2G GPS Tracker Devices GSM Car Pet Smart Watch | eBay
Invoxia GPS Tracker Review - 1st antitheft GPS for bikes & No SIM card