You could additional parameter, lets say the parameter name is sensor_name and this value could be extracted from the method, selectedSensorBean. You also need an identifer in your sensor variable, ex: #{sensor.name}
<p:selectOneMenu value="#{deviceTypeController.selectedSensorBean}">
<f:selectItem itemLabel="Select One"/>
<f:param name="sensor_name" value="#{sensor.name}" />
<f:selectItems value="#{deviceTypeController.lstSensors}" var="fields"
itemLabel="#{fields.sensor}" itemValue="#{fields}"/>
</p:selectOneMenu>