A commercial product which collected all this sensor data for a home security system would be awesome. A natural role for home server. A person with a protection order could monitor for the entry of the evil doer into their space. Or a surveillance system in your garden which would detect the presence of dear and do whatever it takes to keep them from eating your vegetables.
On the personal measurement front, are there detectors that can hear heart beats and respiration in the vicinity? No doubt you can measure weight when a person steps on a door mat that contains pressure sensors. An ultimate nerd moment would be when your sound detection and analysis system sends an alert to the server warning that the person at a specific location is suffering from congestive heart failure.