Sleep position trainer apparatus which is configured to avoid an undesired posture during a sleep period, the sleep position trainer apparatus comprising: - a control unit (CU) which control unit includes a control programme which is programmed to generate an output signal based on at least one received input signal; - at least one sensor (S) for detecting a sleep related event, which sensor is operatively connected to the control unit to provide a sensor signal as a first input signal to the control unit, wherein the sleep position trainer comprises a position sensor for detecting a body posture of a person wearing the sleep position trainer; - an alert unit (AU) for providing an alert stimulus to the user wearing the sleep position trainer apparatus, which alert unit is operatively connected to the control unit to receive the generated output signal from the control unit, whereafter the alert stimulus is generated; wherein the sleep position trainer has a normal operational mode for alerting during a user's sleep period, in which normal operational mode the control unit generates an output signal to the alert unit, and the alert unit generates an alert stimulus when a posture of the body detected by the position sensor corresponds with at least one predefined undesired body posture, wherein the sleep position trainer further comprises a non-movement timer (t1) for timing a non-movement period of the user wearing the sleep position trainer, and characterized in that the control unit (CU) is programmed to send an output signal to the alert unit in case that a posture of the body detected by the position sensor corresponds with a body posture other than the at least one predefined undesired posture when a threshold value of the non-movement timer (t1) of at least 15 minutes is exceeded. - a control unit (CU) which control unit includes a control programme which is programmed to generate an output signal based on at least one received input signal; - at least one sensor (S) for detecting a sleep related event, which sensor is operatively connected to the control unit to provide a sensor signal as a first input signal to the control unit, wherein the sleep position trainer comprises a position sensor for detecting a body posture of a person wearing the sleep position trainer; - an alert unit (AU) for providing an alert stimulus to the user wearing the sleep position trainer apparatus, which alert unit is operatively connected to the control unit to receive the generated output signal from the control unit, whereafter the alert stimulus is generated; wherein the sleep position trainer has a normal operational mode for alerting during a user's sleep period, in which normal operational mode the control unit generates an output signal to the alert unit, and the alert unit generates an alert stimulus when a posture of the body detected by the position sensor corresponds with at least one predefined undesired body posture, wherein the sleep position trainer further comprises a non-movement timer (t1) for timing a non-movement period of the user wearing the sleep position trainer, and characterized in that the control unit (CU) is programmed to send an output signal to the alert unit in case that a posture of the body detected by the position sensor corresponds with a body posture other than the at least one predefined undesired posture when a threshold value of the non-movement timer (t1) of at least 15 minutes is exceeded. <EOS>