Is er een app om je mobiel scherm te locken met de volumeknop?

Ja dat bestaat.
Ik denk dat dit is wat je zoekt.

Fix Broken Power Button
Destil

Of het werkt moet je even proberen.
Let op dat als het niet goed werkt dat je de app moet uitzetten voordat je het verwijderd!

Beschrijving
!No more support from the developer!
Do you have broken power button? This app can save your phone! You can unlock screen by other keys and lock screen using widget.
Details:
- No ROOT required
- Android 2.2 unlocks with VOLUME keys and TRACKBALL
- Android 2.3 unlocks only with VOLUME keys
- Android 3+ works only when slide-to-unlock is disabled
- You can use simple unlock screen with clock to prevent undesired mistaps
- Works mostly just on Nexus One/S. Other devices are experimental!
- The app is open-sourced and it is based on app AnyUnlock. If AnyUnlock works for you, this app will work also.
- English and Czech localization
IMPORTANT:
- DISABLE BEFORE UNINSTALL!
- If you have troubles entering PIN after reboot: disable, enter PIN and enable.
- Don't use app killers, they will kill the app and you won't be able to unlock your phone
- You won't be able to protect your phone with password/pattern
Did I saved your phone? Please donate: https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=PSHU456C862DQ


Link:
https://play.google.com/store/apps/details?id=cz.destil.fixbrokenpb&hl=nl