Apparatus comprises an acceleration unit (100), a processing unit (104) and a display (106) for continuous real time monitoring. The acceleration unit (100) is attached or held by a body region (102) of a mammal comprises a 3D-acceleration sensor (200) and a wireless transmitter (202) for transmitting a measurement signal provided by the acceleration sensor (200) continuously. The processing unit (104) processes the measurement signal continuously in a band of a medically defined movement of the body region, forms a movement index on the basis of a norm of values of acceleration in a first time window, and forms a value(s) of amplitude, and/or a value of frequency of the spatial movement of the body region (102) on the basis of a power spectral density in second time window of a known duration. The display (106) displays said movement index with said value of amplitude, and/or said value of frequency of the spatial movement continuously in real time.
