Any Findster Duo ecossystem consists of at least 1 Guardian module and 1 Pet module - both are necessary to use the system, and here's why.
Findster Duo uses our proprietary MAZE technology - an innovative and exclusive technology exclusively developed by Findster, which allows us to eliminate the need for a cellular connection to obtain the GPS coordinates (hence no monthly fees!). Basically, the Guardian module serves as a gateway between the Pet module and your smartphone. It resends the GPS data acquired by the Pet module to your smartphone via Bluetooth. Because of this, both modules are required in order for the system to work.
For more information, please check the article on how Findster Duo works.