PeakG - G-Force & Motion Meter

PeakG turns your iPhone and Apple Watch into a G-force meter and recorder. See the load you feel, live, then review every moment on zoomable charts and a GPS track map.

Built for pilots and track drivers, and for anyone curious about the forces on a rollercoaster, a ski run or a bike trail.

THREE MODES
• Everyday: total G, the load you feel, wherever the phone sits. Rollercoasters, rides, runs and trails.
• Car: grip in words, like "Braking 0.82 g" and "Right turn 0.91 g", on a grip circle. Mount the phone any way up; PeakG learns which way is forward from GPS.
• Flight: signed load factor, from +4.2 g into the seat to −1.1 g out of it, with climb rate and altitude. Tap Set level in straight and level flight, or let Auto level work it out.

READINGS THAT MATCH WHAT YOU FEEL
A shaken phone can spike past 10 g for a few hundredths of a second. You never feel that, so PeakG doesn't count it: the sensors run at 100 Hz and are smoothed with the 5 Hz filter used to evaluate rollercoaster forces (ASTM F2291). The display stays steady while the recording keeps the detail. Prefer the raw signal? It's one setting away. The one-minute Sensor check shows how accurately your phone reads.

RECORD AND REVIEW
• One tap to record; iPhone keeps recording with the screen locked
• One large chart per channel: pinch to zoom, pan and scrub
• One large chart per channel: pinch to zoom, pan and scrub
• Highlights jump straight to the hardest moments
• GPS track map coloured by G-force
• Peak G, time above your threshold, speed, distance, altitude and climb rate
• Optional haptic alert when you pass your G threshold
• Crash-safe: if PeakG is closed mid-recording, everything up to that moment is kept

APPLE WATCH
Record on your wrist without your iPhone, in all three modes. Sessions are sent to your iPhone automatically, even when PeakG isn't open on either device, and the Watch keeps each one until your iPhone confirms it. Units, modes and alerts stay in sync.

EXPORT EVERYTHING
CSV with real timestamps, full JSON, or GPX for mapping tools. Export a whole session, just the part you've zoomed in on, or several sessions at once. Save a reading anywhere from every 10 ms to every second.

YOUR UNITS
Speed in km/h, mph, knots or m/s. Altitude in metres or feet.

PRIVATE BY DESIGN
No account, no analytics, no ads. Your sessions stay on your devices until you choose to export them.

DESIGNED FOR
• General aviation and aerobatic pilots
• Track days, karting and autocross
• Skiers, snowboarders and mountain bikers
• Rollercoaster and thrill ride fans
• Anyone curious about the forces in everyday life

PeakG is for recreation and analysis, not a certified instrument. Never handle your phone while driving, flying or riding, and always secure it so it can't come loose.

Start recording. See what you feel.