A system for a sensing rotation frequency of a rotatable member and for monitoring health thereof, the system comprising: a rotatable member; and a magnetic speed probe including: a magnet for generating a magnetic field proximate the rotatable member, the magnet being configured such that rotation of the rotatable member causes changes in the magnetic field generated by the magnet; an inductive coil positioned proximate the rotatable member, the inductive coil being configured such that changes in the magnetic field induce a coil current within the inductive coil; and a sensing circuit coupled to the inductive coil, the sensing circuit configured to generate, in response to the coil current, a signal indicative of the rotation frequency of the rotatable member; and characterised by a speed-probe monitor including: a signal generator coupled to the inductive coil of the magnetic speed probe, the signal generator being configured to generate radio-frequency signals that, when conducted by the inductive coil, causes the inductive coil to act as a radio transmitter that radiatively transmits the radio-frequency signals; a radio receiver that is configured to receive the radio-frequency signals radiatively transmitted by the inductive coil; and a health monitor that is configured to determine health of the magnetic speed probe based on the radio-frequency signals received. a rotatable member; and a magnetic speed probe including: a magnet for generating a magnetic field proximate the rotatable member, the magnet being configured such that rotation of the rotatable member causes changes in the magnetic field generated by the magnet; an inductive coil positioned proximate the rotatable member, the inductive coil being configured such that changes in the magnetic field induce a coil current within the inductive coil; and a sensing circuit coupled to the inductive coil, the sensing circuit configured to generate, in response to the coil current, a signal indicative of the rotation frequency of the rotatable member; and characterised by a magnet for generating a magnetic field proximate the rotatable member, the magnet being configured such that rotation of the rotatable member causes changes in the magnetic field generated by the magnet; an inductive coil positioned proximate the rotatable member, the inductive coil being configured such that changes in the magnetic field induce a coil current within the inductive coil; and a sensing circuit coupled to the inductive coil, the sensing circuit configured to generate, in response to the coil current, a signal indicative of the rotation frequency of the rotatable member; and characterised by a speed-probe monitor including: a signal generator coupled to the inductive coil of the magnetic speed probe, the signal generator being configured to generate radio-frequency signals that, when conducted by the inductive coil, causes the inductive coil to act as a radio transmitter that radiatively transmits the radio-frequency signals; a radio receiver that is configured to receive the radio-frequency signals radiatively transmitted by the inductive coil; and a health monitor that is configured to determine health of the magnetic speed probe based on the radio-frequency signals received. a signal generator coupled to the inductive coil of the magnetic speed probe, the signal generator being configured to generate radio-frequency signals that, when conducted by the inductive coil, causes the inductive coil to act as a radio transmitter that radiatively transmits the radio-frequency signals; a radio receiver that is configured to receive the radio-frequency signals radiatively transmitted by the inductive coil; and a health monitor that is configured to determine health of the magnetic speed probe based on the radio-frequency signals received.