System and methods for monitoring and/or controlling nerve activity in a subject are provided. In one embodiment, a system includes electrodes configured to be placed proximate to a subject's skin, and a signal detector configured to detect electrical signals using the electrodes. The system also includes a signal processor configured to receive the electrical signals from the signal detector, and apply a filter to the received electrical signals to generate filtered signals, the filter configured to attenuate at least signals having frequencies corresponding to heart muscle activity during a heartbeat. The signal processor is also configured to identify a skin nerve activity using the filtered signals, estimate a sympathetic nerve activity using the identified skin nerve activity, and further to generate a report indicative of the estimated sympathetic nerve activity. In some aspects, the system further includes a signal generator to deliver the electrical stimulation to the subject's skin.