Context

Given that I stay in a home with five other people and we generally ask each other about the availability of other people in our home, I think it will be highly beneficial for all of us, especially to my housemate living on the first floor, who gets asked about all others if this information availability is ensured whenever it is required. Also, it could highly useful in emergency/ urgency scenarios since if we know that the person is not available at home, we can ourselves do the work or call for outside help immediately. 

There are a couple of precedent projects related to this one which could be found here: 

 http://www.instructables.com/id/Make-An-Simple-Motion-Sensor-Light-PIR/ 

http://ideate.xsead.cmu.edu/uploads/contents/8028/original/homehack.pdf?1486020771