A system for determining an inclination of a first device relative to a user, comprising: a first device including a first orientation measuring unit comprising an accelerometer for measuring an acceleration of the first device and translating the measured acceleration data into an inclination of the first device relative to the earth, wherein the first device is a personal care appliance; a second device associated with the user such that an orientation of the second device is indicative of the orientation of a body part of the user, the second device including a second orientation measuring unit which is an accelerometer for measuring an acceleration of the second device and translating the measured acceleration data into an inclination of the second device relative to the earth; characterized in that the system further comprises: a processing unit located in the first device and arranged to calculate an inclination of the first device relative to the second device by comparing a measured inclination of the first device relative to the earth with a measured inclination of the second device relative to the earth; wherein the first device further comprises a first communication unit , and the second device further comprises a second communication unit , wherein the second communication unit is arranged to transmit the measured inclination of the second device relative to the earth to the first communication unit; and wherein the processing unit is arranged to calculate the inclination of the first device relative to the second device by performing geometric subtraction of the measured inclination of the first device relative to the earth and the measured inclination of the second device relative to the earth. a first device including a first orientation measuring unit comprising an accelerometer for measuring an acceleration of the first device and translating the measured acceleration data into an inclination of the first device relative to the earth, wherein the first device is a personal care appliance; a second device associated with the user such that an orientation of the second device is indicative of the orientation of a body part of the user, the second device including a second orientation measuring unit which is an accelerometer for measuring an acceleration of the second device and translating the measured acceleration data into an inclination of the second device relative to the earth; a processing unit located in the first device and arranged to calculate an inclination of the first device relative to the second device by comparing a measured inclination of the first device relative to the earth with a measured inclination of the second device relative to the earth; wherein the first device further comprises a first communication unit , and the second device further comprises a second communication unit , wherein the second communication unit is arranged to transmit the measured inclination of the second device relative to the earth to the first communication unit; and wherein the processing unit is arranged to calculate the inclination of the first device relative to the second device by performing geometric subtraction of the measured inclination of the first device relative to the earth and the measured inclination of the second device relative to the earth. <EOS>