The worst kind of low battery indicator to have is one that

- Sounds like an alarm clock, a monotone beeping
- Beeps only roughly once per hour but is very imprecise in doing so
- Is coming from a device that is explicitly made to be installed inside a shelf or cabinet
- Is coming from a device that is not in constant use, lasts months if not years on one set of batteries and can easily be forgotten

Anyways, I'm glad I figured out it's the IKEA NFC cabinet lock that's been waking me at night..