The invention relates to an apparatus for monitoring of a body function and/or a body property of a patient having a sensor which determines measurement values with regard to the body function and/or the body property, a unit for detecting a critical condition of the respective body function and/or body property based on the measurement values, a unit for providing alert information to the patient in case a critical condition is detected, preferably optically and/or acoustically, an acknowledgement unit for acknowledging the critical condition and a transmitter for transmitting information with regard to the corresponding body function and/or body property, for example an emergency signal and/or a position information, wherein the transmitter is only activatable in the case, in which after a predefined time period from the detection of the critical condition the acknowledgement unit has not been operated.