A system, comprising: a primary antenna configured to be located external to a subject; at least one processor configured for electrical communication with the primary antenna; an external unit with which the primary antenna and the at least one processor are associated; an implantable device configured to be implanted in the body of a subject proximate to the subject's tongue and configured to modulate the hypoglossal nerve; and a secondary antenna associated with the implantable device; wherein the at least one processor is configured to: receive a condition signal from the implantable device, wherein the condition signal is indicative of a degree of coupling between the primary antenna and the secondary antenna; determine whether the condition signal is indicative of a precursor to sleep disordered breathing; and cause transmission of a primary signal, the primary signal being based on the degree of coupling, from the primary antenna to the secondary antenna associated with the implantable device, to stimulate the hypoglossal nerve, in response to a determination that the condition signal is indicative of a precursor to sleep disordered breathing; characterized in that the processor is configured to cause a metered response based on the determined degree of coupling between the primary antenna and the secondary antenna. a primary antenna configured to be located external to a subject; at least one processor configured for electrical communication with the primary antenna; an external unit with which the primary antenna and the at least one processor are associated; an implantable device configured to be implanted in the body of a subject proximate to the subject's tongue and configured to modulate the hypoglossal nerve; and a secondary antenna associated with the implantable device; wherein the at least one processor is configured to: receive a condition signal from the implantable device, wherein the condition signal is indicative of a degree of coupling between the primary antenna and the secondary antenna; determine whether the condition signal is indicative of a precursor to sleep disordered breathing; and cause transmission of a primary signal, the primary signal being based on the degree of coupling, from the primary antenna to the secondary antenna associated with the implantable device, to stimulate the hypoglossal nerve, in response to a determination that the condition signal is indicative of a precursor to sleep disordered breathing; characterized in that the processor is configured to cause a metered response based on the determined degree of coupling between the primary antenna and the secondary antenna. receive a condition signal from the implantable device, wherein the condition signal is indicative of a degree of coupling between the primary antenna and the secondary antenna; determine whether the condition signal is indicative of a precursor to sleep disordered breathing; and cause transmission of a primary signal, the primary signal being based on the degree of coupling, from the primary antenna to the secondary antenna associated with the implantable device, to stimulate the hypoglossal nerve, in response to a determination that the condition signal is indicative of a precursor to sleep disordered breathing; characterized in that the processor is configured to cause a metered response based on the determined degree of coupling between the primary antenna and the secondary antenna.