There’s a chip on the Galaxy S III called the STMicroelectronics LSP331AP, which is a pressure sensor. STMicroelectronics has decided to explain it to us, since it’s their new generation of pressure sensors. The chip is piezoresistor-equipped that uses pressure to track altitude. Even though it’s just a chip in a cell phone, it’s accurate enough to tell when you’re traveled between two floors. It can also work between 32,800 feet above and 5,900 feet below sea level. This has a lot of possibilities of course, including use in Google Maps’ indoor navigation (like mall maps) and sports like skydiving. Let’s hope these sensors go mainstream, and Samsung, thanks for pioneering them.
Except, of course, one can't determine altitude by pressure alone because the barometric pressure is constantly changing. I wouldn't expect this chip to be able to tell the exact altitude, but it should be able to tell a ride up an escalator or elevator because that air pressure change is much faster than normal barometric pressure changes. But walking from one room to another might also fool this type of 'altitude' detection. If you notice a significant draft through the doorway then the air pressure is higher where the draft is coming from that where the draft is going to. This would also show as a pressure differential to the chip.
So, because of all the nastiness (and others) that I've described above, I think using a pressure sensor to determine altitude is foolish. But, with a good GPS signal to give an accurate altitude this chip could work as a decent weather barometer for local weather prediction. Build an app around that and you might have something.
Although, if one wants to launch your SIII on a stratospheric balloon, once you get above the weather (and above where the GPS should stop working by law), the local variations in pressure aren't as big and one can actually use the pressure for altitude. Hobby balloonists rejoice!
Oh crap. I just re-read the article, and that 32,800 feet above sea level limitation means this chip would hit it's maximum altitude (minimum pressure) long before the GPS cuts out. Hobby balloonists, you still have to calculate maximum altitude instead of read it, or continue reading your digiquartz paroscientific barometers (see http://www.paroscientific.com/pdf/2000.pdf ) by frequency on the headset mic input... That is if buying an SIII doesn't kill your budget so much you can't afford one of those niftily expensive paroscientific barometers.