Embodiments of the present invention are directed to a physiological monitoring device which is configured to record signals that reflect blood flow and/or blood pressure, and which may also record ECG signals. In one embodiment, a portable monitoring device comprises a plurality of impedance electrodes configured to be coupled to a patient's body and to generate an AC current with an electrical field to detect local electrical impedance of a portion of the patient's body encompassed by the electrical field, the local electrical impedance being a surrogate measure of local blood flow of the portion of the patient's body. At least a portion of the portable monitoring device is configured to be insertable subcutaneously into the patient's body.