home automation: presence achitecure

each person signs into a room as he walks in and signs out as he or she walks out. each room will have user preferences, what should be done when that person enters the room, play song, read news, set room to certain settings etc
the best case scenario is each person has a chip which is automatically detected, and user is signed on.
I am thinking of using jabber, and presence as the room, so when adarsh walks into bedroom, his bedroom presence is logged in.
we will need to integrate this with general mood also, say its evening, on a dark gloomy day, or a bright sunny day in summer, then we can corelate to which song to play. ofcourse the person should be able to set their own mood.
requirements coming out from this meeting
1) lets look at jabber
2) program for multiple people (what happens when multiple people are in a room, should we automatically play romantic music when adarsh and his girlfriend are in the same room, what happens when girlfriend changes)
3) are going for a client server or a peer to peer network
4) need a better way to caputre requirements and turn them into design
5) need to decide on technology java, perl or something else
6) how do we manage rules