Global Navigation Satellite Systems (GNSS) are exploited in a wide range of applications and its reliability and accuracy are more critical than ever. The weak GNSS signals are extremely susceptible to intentional or unintentional interference. The Joint Research Centre has explored the potential of leveraging the ubiquitous presence of Android smartphones for interference monitoring. Automatic Gain Control (AGC) measurements provided by the Android GNSS API are used for this purpose. A proof-of-concept including an App to collect the data and a back-end server for the processing has been developed and tested. The proposed approach demonstrates the potential to detect both intentional and unintentional interference. However, the approach has limitations, such as small AGC variations that cannot always be linked to GNSS interference, and significant differences between smartphone models which need to be considered for effective crowdsourcing.