A patient-monitoring system comprising a computer monitor including a computer processor and disposable patient-monitoring device configured to be attached to tubing in fluid communication with a patient's blood vessel, and configured to be attached in electrical communication with the computer processor, the patient-monitoring device comprising: at least one pressure sensor configured to be in fluid communication with a patient's blood vessel through a fluid-receiving region in the pressure sensor and configured to be in electrical communication with the computer processor, the pressure sensor being configured to sense a pressure wave in the patient's vasculature and being configured to transmit at least one patient-information electrical signal to the computer monitor that indicates a physiological parameter of a patient; a temperature sensor configured to sense ambient temperature at the disposable patient-monitoring device the temperature sensor in electrical communication with a signal generator that is configured to send a gatekeeper electrical signal to the computer processor that indicates the ambient temperature at the disposable patient-monitoring device, outside of the fluid region, wherein the computer processor is configured to confirm that the disposable patient-monitoring device is attached in electrical communication with the computer processor by determining whether the ambient temperature indicated by the gatekeeper electrical signal is within a predetermined range of standard temperature values, the gatekeeper electrical signal not including diagnostic or physiological information about the patient; wherein the information conveyed by the patient-information electrical signal not required to be calibrated or modified by the gatekeeper electrical signal. at least one pressure sensor configured to be in fluid communication with a patient's blood vessel through a fluid-receiving region in the pressure sensor and configured to be in electrical communication with the computer processor, the pressure sensor being configured to sense a pressure wave in the patient's vasculature and being configured to transmit at least one patient-information electrical signal to the computer monitor that indicates a physiological parameter of a patient; a temperature sensor configured to sense ambient temperature at the disposable patient-monitoring device the temperature sensor in electrical communication with a signal generator that is configured to send a gatekeeper electrical signal to the computer processor that indicates the ambient temperature at the disposable patient-monitoring device, outside of the fluid region, wherein the computer processor is configured to confirm that the disposable patient-monitoring device is attached in electrical communication with the computer processor by determining whether the ambient temperature indicated by the gatekeeper electrical signal is within a predetermined range of standard temperature values, the gatekeeper electrical signal not including diagnostic or physiological information about the patient; wherein the information conveyed by the patient-information electrical signal not required to be calibrated or modified by the gatekeeper electrical signal.