I have an additional suggestion for the battery cover - see the attached picture for clarification.
On the side that slides out you can add some affordances indicating the sliding direction for either opening or closing/locking.
This would work better as an embossed ridge pattern and symbols (a lock maybe?) rather than raised ridges.
Embossed means adding material to the mould but there would be less danger of having the Pyra "sit" tilted on a flat surface.