An electronic device uses one or more infrared sensors to detect infrared light from a person's body (e.g., a user's finger) to initiate a function of the electronic device. According to an implementation, the housing of the electronic device includes a flexible portion that opens an aperture in response to external pressure (e.g., a user pressing down on the flexible portion) to allow infrared light from the person's body to reach an infrared sensor. When the infrared sensor detects the infrared light, it generates a signal in response. A processor of the electronic device receives the signal and, in response, initiates a function of the electronic device. The function may be any function that the electronic device is capable of performing, such as a power-on function, a camera function, changing the speaker volume, and launching an application.