When HN users recommended it
1 HN user recommended this in 2020, in one comment.
20072026
Each tall tick is one HN user's first recommendation. A short tick is the same user again. Click a tick to jump to the comment.
1 HN user recommended this in 2020, in one comment.
Each tall tick is one HN user's first recommendation. A short tick is the same user again. Click a tick to jump to the comment.
For fixed locations, there are cheap P-wave detection earthquake alarms based on mechanical pendulums that will give seconds of warning.
Example: https://www.amazon.com/dp/B001D8NMY4
Also, cat alarms: https://youtu.be/VJ-p9qOhBv4