The invention relates to a method for extending an application in a client device. The system comprises a magnetic deflector operable to create a magnetic field, and a pole piece assembly at least partly accommodated within the magnetic field. A secondary side switch controller controls switching of the forward transistor and the catch transistor without communication from the primary side. In the event illegal activity is indicated, the method includes taking some corrective action such as producing an operator alert to the potential illegal activity. These compounds can be used in the treatment of hyperglycaemia-related pathologies.