Phyphox, a free open source app from Germany's RWTH Aachen University, reads the accelerometer, gyroscope, magnetometer, microphone, light sensor, GPS, and barometer inside most modern phones as working measurement tools.
A modern smartphone already carries an accelerometer, gyroscope, magnetometer, microphone, ambient light sensor, GPS receiver, and, on many models, a barometer. Phyphox, short for Physical Phone Experiments, is a free and open-source app developed at RWTH Aachen University by physicists Heidrun Heinke, Sebastian Staacks, and Christoph Stampfer that treats that hardware as a working instrument cluster. A recent hands-on test by ZDNET's Jack Wallen, run on a Pixel 9 Pro, walks through roughly 35 in-app experiments, and the numbers it produces look like real measurements rather than party tricks.
The key insight is that the sensors were always there. Phone makers added them for screen rotation, step counting, navigation, and image stabilization. Phyphox simply reads them the way a laboratory would. The accelerometer returned an angle of tilt: Wallen measured a stair at negative 32 degrees, the kind of reading a civil engineer might use to check a handrail. The microphone doubled as a spectrum analyzer, returning a 93.75 Hz peak from the hum of a typical office. The barometer recorded 999.524 hectopascals of atmospheric pressure. The light sensor measured 0.177 in a dim room and 3.4 against a monitor. The magnetometer told apart two Steinberger guitar pickups. None of these tests required any extra hardware, and the same experiment list runs on iOS, with sensor coverage depending on the device.
The app is academic in origin. RWTH Aachen's 2nd Institute of Physics built Phyphox as a teaching tool, and the project has accumulated a stack of education awards, including the 2020 Ars legendi-faculty prize from the Stifterverband and the German physics, math, and chemistry societies, the German Physical Society's 2019 AGPP teaching award, the 2019 Archimedes prize from the German teachers' association MNU, and a student-led RWTH teaching award in 2018. Funding flows through RWTH's Exploratory Teaching Space, the BMBF's Qualitätsoffensive Lehrerbildung program (LeBiAC2), and the Hans Hermann Voss Foundation. That provenance matters: the app is free, ad-free, and open-source, and the people who wrote it have an academic interest in how the data is collected rather than a venture capital interest in selling the user something else.
Two features extend Phyphox beyond a fixed menu of experiments. First, the app can run an experiment from a desktop browser, so a teacher can hold a phone in front of a class and the live graph appears on a projector. Second, a web-based custom-experiment editor lets users wire sensors to graphs, math operations, and exports without writing code. The open catalog covers accelerometers, gyroscopes, magnetometers, pressure, light, proximity, GPS, and microphone inputs, with sensor coverage varying by phone model. The Pixel line includes a color sensor, recent iPhones carry barometers, and some budget Android phones skip the barometer entirely.
The honest limits deserve airtime. Consumer phone sensors are not lab instruments. Their absolute accuracy, calibration drift, and sampling rates fall well short of dedicated equipment, and ZDNET's measurements are single snapshots in one reviewer's environment rather than benchmark results. Phyphox is a teaching, curiosity, and field-screening tool. It is not a substitute for a calibrated accelerometer, a laboratory spectrum analyzer, or a barometric altimeter, and treating it that way would be a category error. The "35 experiments" count is the reviewer's enumeration on a Pixel 9 Pro, not a fixed product spec, and the actual set shifts with the sensors your particular phone happens to carry.
Treated on its own terms, though, the app does something that matters. It turns a device a reader already owns into a credible first pass at measurements that would otherwise require a bag of instruments, a budget, or a university lab. A high school physics class can collect the same data Wallen did. A citizen scientist can log barometric pressure on a hike. A guitar player can compare pickup output. The cost of entry is a free download from Google Play or the iOS App Store, and the only prerequisite is owning a phone that has the relevant sensors in the first place.
For educators and curious readers, the watch item is whether the open catalog keeps growing and whether the custom editor matures into something a non-programmer can use for serious projects. The Aachen team has been steady about both, and the underlying sensor hardware inside phones is only getting better with each generation.