Sensefield — Phone Sensors

Your iPhone is full of scientific instruments. Sensefield turns them into something you can actually look at. Seven of them, each on its own screen, with a big readout, a chart that moves as you move, and a plain explanation of what you are seeing. All seven are free. MOTION • Accelerometer — every push, knock and wobble turned into numbers, with a tilt ball that rolls with gravity as you tip the phone. Rest it on a washing machine and watch the spin cycle arrive. • Gyroscope — how fast you are turning, on all three axes at once. FIELDS • Magnetic Field — wave the phone past a speaker, a laptop, or a fridge door and watch the reading jump. Underneath it all sits the Earth's own field, the one compasses have been using for centuries. • Compass — magnetic and true north on a live dial. ENVIRONMENT • Pressure & Altitude — take it into a lift and watch the pressure drop. It notices a single flight of stairs. • Sound Level — how loud it is right now, with the frequencies moving underneath. RADIO • Bluetooth — the devices quietly announcing themselves around you, how strong each one is, and what it is actually broadcasting. RECORDING Pick what to record, set a time limit, press record. Only the instruments you chose will run, so a recording costs one instrument's worth of battery rather than seven. When it stops you get the whole session as charts, with the range of each reading beside it. Recording is free: one instrument at a time, up to five minutes, with the same charts at the end. SENSEFIELD PRO One payment, once. Not a subscription. Pro records every instrument together on the same clock, runs for up to an hour, and exports what you captured as CSV — one file per instrument, straight into Files, Mail, or wherever else you send things. Open them in Numbers, Excel, Python, or MATLAB. If you bought Sensefield when it was a paid app, Pro is already yours. NOTHING LEAVES YOUR PHONE No account. No sign-in. No ads. No tracking. No servers. Sensefield collects nothing, because it has nowhere to send it. Every instrument works in airplane mode. INSTRUMENTS STAY OFF UNTIL YOU ASK Pressure, sound, compass and Bluetooth each need your permission, so they start switched off. Open the app and the motion instruments are already running, with no dialogs at all. Switch the others on when you actually want them. HONEST ABOUT WHAT IT CANNOT DO Every app in this category promises more than the hardware can give. Here is where the edges are. • The sound meter is not calibrated. iPhone microphones vary by model and by case, so no app can honestly hand you a real decibel figure. Sensefield shows a relative level and says so, rather than printing an official-looking number it cannot stand behind. • Signal strength is not distance. Bluetooth tells you roughly how close something is, never how many metres away. • Your car stereo will not appear. iOS shows apps only the newer Low Energy devices and hides the rest — from every app, not just this one. • Recording needs the app open and the screen on. iOS gives no app a way to keep reading motion sensors in the background. • Not every iPhone has every sensor. Sensefield tells you what is missing instead of inventing a number to fill the gap. • Pro unlocks what is already in the app. Nothing is downloaded, nothing expires, and nothing stops working if you never buy it. Sensefield works in light and dark, follows your text size, and is labelled throughout for VoiceOver. For the curious, for students and teachers, for makers and engineers, and for anyone who has ever wondered what their phone can actually feel.