J-K Bike - Mechanical Disaster Prevention is an open-source (EUPL-1.2) Android app by Jan Exner. The APK we host is 5.2 MB, it needs Android 10 or newer, and it declares 7 permissions.
The file on this page is J-K Bike - Mechanical Disaster Prevention 4.2.1, 5.21 MB, and it installs on Android 10 and newer.
We compared the signing certificate of this build with the certificate recorded the first time com.exner.tools.jkbikemechanicaldisasterprevention.light entered the site, and published both the file's SHA-256 and the certificate's fingerprint above so you can check the download yourself. That comparison says the file was not repackaged by someone else; it is not a review of what the app does.
The manifest declares 7 permissions, including access to the camera. Android asks you to approve those the first time the app needs them.
Its licence is EUPL-1.2. We took this build from F-Droid, and the source for this exact version is linked below.
We do not show a star rating or an install count for this page: we have no measured figure for either, and a number we cannot source is worth less than an empty field.
- Version
- 4.2.1
- Size
- 5.21 MB
- Requires Android
- API 29
- Package
- com.exner.tools.jkbikemechanicaldisasterprevention.light
- Signature checked on
- Sep 18, 2026
- Where this file came from
- F-Droid
- Licence
- EUPL-1.2
- Source code
- Source for this version
File SHA-256: 780302301840e3071c3291316b0c317671432f7155ea660bf2ca40877c128b7d
Signing certificate (SHA-256): 07a89b9b74e8d980673671912166ace204c2f73523cd631b933cb4f77ac4a2cf
We check that this file carries the same signing certificate as earlier releases of the same package. That shows the APK was not repackaged by someone else — it is not a security review of the app.
Declared permissions
- POST_NOTIFICATIONS
- INTERNET
- WAKE_LOCK
- ACCESS_NETWORK_STATE
- RECEIVE_BOOT_COMPLETED
- FOREGROUND_SERVICE
- CAMERA
Screenshots
