I need a cross-platform smartphone app that captures a car’s 0-to-100 km/h sprint using only the device’s built-in accelerometer. The core flow is simple: open the app, add basic vehicle details, place the phone securely in the vehicle, press “Start”, drive, and see an accurate time once 100 km/h is reached. Branding & UI The visual language must stay minimal and clean, with my branding which I will share with you. No user sign-up is required; the experience should feel instant from install to first run. Core functions • Real-time detection of movement, speed, and distance until exactly 100 km/h is logged. • Audible cue or haptic feedback when timing starts and stops. • Automatic saving of each session so the driver can review a history of past runs (date, time, conditions, and final result). • Basic settings panel to toggle units (km/h ↔ mph) and sensor sensitivity. Deliverables • iOS build (TestFlight ready) and Android APK / Play Console bundle. • Source code with clear comments plus a short README covering sensor calibration logic. • Lightweight branding pack: app icon, splash screen, and colour/typography guide aligned to the minimal style and my branding. • A brief note on accuracy testing methodology so I can replicate your results. Acceptance criteria • Timing variance stays within ±0.30 sec when compared to an external GPS-based timer at three different speeds. • App launches to first action screen in under two seconds on devices from the last four OS versions for both platforms. • No crashes or major UI glitches during a 10-run stress test. - Ability to extend the app to record 0-60km/h, 60-110km/h, and 0-400m. Preferred stacks are React Native or Flutter, but I’m open to efficient native builds if that speeds up sensor access. Let me know which route you plan to take, any libraries you’ll rely on, and roughly how long the initial prototype will need.