Wearable accessory for monitoring whether user is looking at portable electronic device

An electronic device comprising:

• a processor;
• a display coupled to the processor;
• a light receiver coupled to the processor and located on a same surface of the electronic device as the display, the light receiver able to produce an output as a function of an incident light intensity of light incident on the light receiver, the light having been transmitted from an accessory paired to the electronic device, the light having been transmitted generally in a direction normal to a face of a person wearing the accessory;
• and
• a memory coupled to the processor, where the memory is to store indications of a first set of one or more behaviors, indications of a second set of one or more behaviors, and code which, when executed by the processor, causes the electronic device to perform the first set of one or more behaviors in response to a first change in the output as a function of an increase in the incident light intensity, and causes the electronic device to perform the second set of one or more behaviors in response to a second change in the output as a function of a decrease in the incident light intensity.