I always was annoyed that my garmin etrex30 has no software keylock. During walks I keep the gps in a pocket or in a bag. Because there is no possibility to lock the keys and especially the joystick the device always switched the menu or even set way points unintentional.
To avoid this I designed a hardware keylock, which additionally acts as cover for the etrex30. With the attached cover the full display is visible.
I already tested the cover during a three day hike and was very satisfied with my new keylock cover.