What's My Sensor?

Your phone is full of sensors. What's My Sensor? shows you all of them. It lists every sensor the hardware reports, tells you what each one is for in one plain sentence, graphs what it is reading as you move the phone, and puts the motion sensors to work as a spirit level and a compass. WHAT YOU SEE Every sensor on the device, grouped into motion, position, environment, body and other. Tap one for its live reading, a graph of the last few seconds with one line per axis, the lowest and highest value it has reached, an explanation of what it measures, and the specification the phone reports for it: maximum range, resolution, power use and how fast it can update. Pause the graph to read a peak off it, or reset it to measure again. SPIRIT LEVEL Lay the phone on a shelf or a table and a bubble shows which way it slopes, in tenths of a degree. Stand it on an edge and it becomes a straight edge for a picture frame or a door. It switches between the two by itself. Set as level takes any surface as your zero, which also takes out the tilt of a camera bump. COMPASS A magnetic compass steered by the phone's own sensor fusion, the same source the system compass uses. It reads where the top of the phone points when it lies flat and where the back points when you hold it up, with a dial that turns so north stays north and a nudge when the magnetometer needs calibrating. It points to magnetic north, because true north would need your location, and this app does not ask for it. Readings are labelled and carry their units, so 9.81 m/s² on the Z axis means something rather than being a bare number. NOTHING IS HIDDEN Sensors that have not fired yet still appear, with a note that they are waiting. That matters for sensors like the step detector and significant motion, which only report when something happens. Other sensor apps make them look like missing hardware. Sensors the phone cannot read are gathered at the bottom of the list, still there to open and explain. WHAT IPHONE CAN AND CANNOT SHOW iOS gives apps the accelerometer, gyroscope, magnetometer, gravity, user acceleration, device attitude and the proximity sensor. It has no public way to read the light sensor, the thermometer or the humidity sensor, and the barometer and step counter sit behind the Motion and Fitness permission, which this app does not ask for. Those sensors are still listed and still explained, gathered at the bottom with a note that they cannot be read here. Knowing what your phone has is worth something even when the reading is out of reach. WHAT IT DOES NOT DO No permissions. No internet access. No analytics, no ads, no accounts, no data collection of any kind. The app reads sensors and draws numbers on the screen. That is the whole app. GOOD FOR Checking a phone before you buy it second hand. Hanging a picture straight. Finding north on a walk. Working out why auto brightness or the compass misbehaves. Catching the peak of a knock or a shake. Seeing whether a repair fixed a proximity sensor. Teaching someone what a gyroscope actually does. Developers checking what a device really reports. Light and dark, with a palette designed for it.