PressureNet (Acquired by Sunshine)
Track atmospheric pressure changes over time
PressureNET is a project by Canadian company Cumulonimbus that uses a smartphones built-in barometric sensor (currently offered in several Android phones and used mainly to improve location data) in combination with the companies app to collect atmospheric pressure data from users around the world.
The end goal of this collection process is to create more accurate local thunderstorm and short-term weather forecasting to the public and offer academic researchers new data points beyond what the widely distributed sensor systems available today can produce.
At the moment pressureNET users are contributing close to 300,000 measurements per day to the service and a real-time dataset has recently been made available to researchers for calibration and integration into their projects via an API.
A user can manually annotate and submit weather conditions for their current location to the service and are able to control their data/location sharing preferences on a granular level from completely public to only offered to certain research groups.
The project is being released under an open source license (GNU GPL), and with new models of smartphones being shipped with an increased number of integrated sensors (The Galaxy S4 can collect readings for temperature, light intensity, pressure, magnetic flux and humidity levels) you can be certain that more accurate data will be collected using this type of crowdsourced process in the future.