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No. Every reading comes from your phone's own accelerometer, computed live on the device. There's no Bluetooth sensor to buy, pair, or keep charged.

A level check runs first because a tilted phone contaminates the vertical acceleration reading with a gravity component before you even start. Set the phone flat on the measured surface and re-check if the level screen flags it.

Consumer MEMS accelerometers have a real noise floor, and low-amplitude floor vibration can sit close to it. Try a firmer excitation (a proper heel drop, not a light tap), keep the phone still and flat during capture, and compare the peak against the RMS acceleration reading rather than reading the chart alone.

No. It's a simplified reference comparison for engineering judgment only — not a certified calculation, and not a pass/fail determination. It does not replace a licensed engineer's judgment.

Free includes live time-domain and FFT view with peak-frequency detection. Pro adds power spectral density analysis, velocity and displacement integration, CSV export, PDF reports, and unlimited saved sessions.

Open the session from History, then use the CSV or PDF button under Output. Both go through your phone's normal share sheet, so you can save, email, or send them straight to your project files.

No. Sessions, waveforms, and reports stay on your device unless you export or share them yourself. Heel Drop has no account and no cloud sync.

Subscriptions are managed by the App Store or Google Play, not inside Heel Drop. On iOS: Settings → your name → Subscriptions. On Android: Play Store → profile icon → Payments & subscriptions.