The barometer data is for sure noisy, and must be cleaned and quality controlled. But that is possible to do, has been for 10 years now (there are published papers and demo apps that can do it). For one, rate of change of atmospheric pressure is pretty much the same inside as out, your main challenge for the raw value to be correct is user elevation. That can be corrected in quality control as well.

Plenty of work has been done on this front, and it can be demonstrated that you can assimilate the smartphone pressures into weather models and get some good results. It is hard, of course, and I’m not sure personally how much better the forecasts get. But it’s absolutely possible.