A hemodynamic sensor system, comprising a sensor implant (102, 102a, 102b, 102c, 102d, 102e, 102f) configured to be implanted in patient tissue adjacent a target blood vessel, wherein the sensor implant comprises: a housing having a housing axis; at least one tissue fixation feature on an outer surface of the housing; at least two ultrasound transducers disposed in the housing along the housing axis with a known distance along said axis between the ultrasound transducers, each said ultrasound transducer positioned to detect a change in diameter of the target blood vessel in response to a cardiac pulse and produce signals representative of detected changes in diameter; at least one accelerometer disposed in the housing configured to detect movement or changes in position of the patient and produce signals representative of said movement or changes in position; a control module disposed in the housing configured to detect timing of and process the signals from the ultrasound transducers and the at least one accelerometer to produce a data stream from which pulse wave velocity for the target blood vessel and patient blood pressure can be calculated; a communication module disposed in the housing configured to transmit said data stream to an external receiver; a power source disposed in the housing operatively connected to power the sensor implant; and wherein the system further comprises an external control module adapted to wirelessly receive the data stream transmitted by the communications module and adapted to calculate pulse wave velocity and patient blood pressure based on the data stream or to transmit the data stream to a networked computing device configured to calculate the pulse wave velocity and patient blood pressure based on said data stream. a housing having a housing axis; at least one tissue fixation feature on an outer surface of the housing; at least two ultrasound transducers disposed in the housing along the housing axis with a known distance along said axis between the ultrasound transducers, each said ultrasound transducer positioned to detect a change in diameter of the target blood vessel in response to a cardiac pulse and produce signals representative of detected changes in diameter; at least one accelerometer disposed in the housing configured to detect movement or changes in position of the patient and produce signals representative of said movement or changes in position; a control module disposed in the housing configured to detect timing of and process the signals from the ultrasound transducers and the at least one accelerometer to produce a data stream from which pulse wave velocity for the target blood vessel and patient blood pressure can be calculated; a communication module disposed in the housing configured to transmit said data stream to an external receiver; a power source disposed in the housing operatively connected to power the sensor implant; and wherein the system further comprises an external control module adapted to wirelessly receive the data stream transmitted by the communications module and adapted to calculate pulse wave velocity and patient blood pressure based on the data stream or to transmit the data stream to a networked computing device configured to calculate the pulse wave velocity and patient blood pressure based on said data stream.