A wireless pressure sensing unit (20) comprises a membrane (25) forming an outer wall portion of a cavity and two permanent magnets (26,28) inside the cavity. One magnet is coupled to the membrane, and at least one magnet is free to oscillate with a rotational movement. At least one is free to oscillate with a rotational movement. The oscillation takes place at a resonance frequency, which is a function of the sensed pressure, which pressure influences the spacing between the two permanent magnets. This oscillation frequency can be sensed remotely by measuring a magnetic field altered by the oscillation. The wireless pressure sensing unit may be provided on a catheter (21) or guidewire.