https://techcrunch.com/2018/06/01/count-your-bees-with-this-raspberry-pi-project/

Bees need all the help they can get. Thus programmer Mat Kelsey created a bee counter to see just how many of his winged honeymakers are hanging out in his hives. His system, which uses a Raspberry Pi and a machine learning algorithm that recognizes the number of individual bees entering a hive, is used to see bee trends over time and see just how the bees are faring.

“The first thing I thought when we setup our beehive was ‘I wonder how you could count the number of bees coming and going?'” wrote Kelsey. “After a little research I discovered it seems no one has a good, non-intrusive system for doing it yet. It can apparently be useful for all sorts of hive health checking.”