I have to say the presence sensor is nice for things like backpacks and purses, but when it comes to putting it on your keyring, the thing is huge!
I noticed it uses a CR2032 inside and that is taking up the majority of the board space. Around it, however, seems to be more plastic than is really necessary. I think if you went to a super durable plastic you could shrink the overall size by 1/3. Perhaps later on, moving to two CR1632’s side by side wired in parallel could take the size even smaller.
Presence Sensor vs Actual Electronics Inside