What is the best way, using technology, to discern whether someone has gone from an awake state to a sleep state. Ideally, this would be something passive and non invasive/not limited to the room or location the person is in.
Ideally this thing would be:
3) easy to acquire
4) utilising the sensors of an existing hardware device, like a mobile phone
5) if it's an existing hardware device, it should have an API that can be used for developing/doing something useful with the awake/asleep data
6) if it's not an existing hardware device, and rather a novel method you've been able to think of, then it should be easily programmable. I don't want to have to import moonrock for one of it's inner components or something.
Think out of the box!