A sexual interaction device for use as an input device for a virtual reality erotic application comprising a body part engaging portion (6, 9, 11, 13, 15) and a distance measurement unit (5). In order to allow for a reliable synchronisation between the user's motion and a virtual environment, it is provided according to the invention that the distance measurement unit (5) comprises an ultrasonic sensor (1) assembly operatively coupled to the body part engaging portion (6, 9, 11, 13, 15).
