It is useful to have one's cellphone behave differently in
different locations - e.g. ring loudly when outdoors,
softly
in the office, or vibrate when in a pocket.
GPS can be used for some of these situations, but isn't
as
useful indoors or for very small changes in location.
Small, clearly
marked paper mats could be left in various
locations - office desk, office drawer, car cubbyhole,
bedside table. The cellphone's built-in camera could
identify which mat it had been placed on by reading a
special pattern printed thereon. The cellphone could
then
be instructed on how to behave on each mat:
Office desk --> ring quietly if called
Office drawer --> keep quiet
Car cubbyhole --> look for bluetooth car kit, or take a
message
Bedside table --> wake me up in time for my first
meeting