A portable spot-check system configured to assess the validity of a measured physiological parameter. The spot-check device can take into consideration a variety of factors to determine whether a valid measurement exists. For instance, the considerations can include signal stability, interference, signal IQ, patient movement, sensor position, timing of that measurement, comparison to previous or acceptable measurements, cancellation of measurement by the patient, confidence of the measurement, etc. The spot-check device can track a number of valid measurements. In some instances, the spot-check device is configured to provide a specified number of available measurements. If a valid measurement is recorded, the spot-check device can decrement the remaining number of available measurements.