A wearable device for an operator to wear upon the wrist, for automatically detecting the onset of degraded performance in the operator; and methods for using such a device. The device utilizes technologies such as surface Electromyography to non-invasively determine the gripping strength of the operator on an operating handle, such as a steering wheel. False positives are eliminated by performing a psychomotor vigilance test (PVT) to confirm a detected onset of degraded performance or to filter out a spurious or anomalous detection of the onset of degraded performance. In other embodiments, a degraded performance notification is sent to a remote server along with the operator's current location to provide a remedial location-based response to relieve the onset of degraded performance. In still other embodiments, a dedicated GPS navigation device provides location-based information to relieve the onset of degraded performance.