Why GPS Tracker need a SIM card ? Why gps tracker need sim card? --GPS device is a mini Featured phone system , just without the keyboard .GPS device system consist of mini phone system+GPS modue +Wifi modue.GPS device work with smart phone app and Cloud server , all GPRS communications via. Sim card through Operator Cellular 's network. It's available for global real time and real Googlemap tracking if the sim is available for international roaming. GPS work with smart phone app is phone to phone. --Any GPS Tracker has a receiver to triangulate its own position from the satellite signals. All the GPS trackers need a SIM card in order to achieve connectivity. SIM cards are what allow location transmission, sending audio data, and receiving commands to turn on audio and other advanced features.