I had to do some boring pressure measurements today at uni. After calibrating the big (about a meter tall) old barometer in the lab we got a reading of 0.998 (+/- 0.002) bar.

Have been interested for a while in the accuracy of the pressure sensor on my phone, so I compared it: it was reading 0.9976 bar. Quite impressive!

The Galaxy S4 has a pressure sensor? Can it make phone calls too?

I don't think the pressure sensor can, but the phone bit does that quite well (sometimes).

Seems a lot/most android devices since about 2012 have a barometer chip chucked in. Have a look in the app store for barometer apps.

Presumably it's used to track altitude changes when using navigation/tracking/NSA apps.

Nexus 5 has one too by the looks of it.

The iPhone has one too, apparently. At least there are apps for it.

But barometric pressure is related to weather. Phones apparently determine altitude based on GPS satellites. So fuck knows why they would have a 'barometer chip'.

GPS altitude is inaccurate and add slow. Although you couldn't establish accurate height without knowing local surface pressure at that given time, you could get a rough estimate (speeding up gps locking) and you can track changes in altitude quite well.

I've just ordered a pressure sensor for my RPi. Another thing to add to my chart.

You need to put a page on your website with one of these, linked to the pressure history:

Kos is right, they use it for a more accurate altitude reading. If you compare results from tracking a bike ride (for example) on a phone without the barometer it's quite a lot different to with.

Maybe you should adapt it to read pressure between two surfaces - like, say, between a speaker and what it's sitting on  :O)

That is pretty impressively accurate for something that is stuffed in a mobile phone. Haven't all these sensors in mobiles made gyros and accelerometers and such cheaper for other things?