An automatic monitoring and sensing apparatus is provided for detecting an intruder or a person whose presence is undesired for one reason or another. According to one aspect of the invention, a method and apparatus are provided for automatically monitoring an environment for the presence of a person, and the invention issues an alarm when the environment changes while the person is still present. For example, the invention is capable of detecting a person in an unexpected or dangerous location in the environment, such as a baby or small child who has been left alone in an automobile. The invention initiates remedial action to safeguard the person. In another aspect, the inventive method and apparatus automatically monitors an environment that is intended to be kept secure, such as an environment where a computer system is installed, wherein the apparatus initiates a safeguarding action such as a pre-emptive automatic back-up of data in the computer system.