This invention relates to a device for detecting the curvature change of the skin surface of a human or an animal subject, comprising a sensing unit and a processing unit. The device can be used for monitoring distention level of the bladder of the subject and so parents may find it useful for toilet training their children by knowing the status of bladders of their children from the device. It is also suitable for other people such as patients suffering from uncontrollable urination, physically disabled patients and/or comatose patients, and even pet owners.
