GF-21 GPS Tracker Test /Review

. This GPS tracker cannot work if a SIM card is not inserted. It can work with or without the mobile APP, so you can have real-time tracking either using SMS or the mobile APP available for Android and iOS. 2. Only GSM SIM card works in this model. GPS locator 3. Please make sure GSM SIM card supports making calls, sending messages, GPRS network. 4. There will be an extra cost of data usage when you use with the SIM Card.