I think I spent less then $6 each with free shipping and today two tiny boxes packed in a plastic bag showed up on the porch.
They connect to zigbee2mqtt with no trouble on the first try and seem to be fully suported by z2m. Quite a few controls are exposed.
I dismantled one and yes it really is a radar and not PIR and it really is powered by two AAA batteries.
These units will not do “presence detection” in a large room, they are motion sensors and do not seen to detect human micro motions like breathing. But they were not advertised to do that. These will be used for close-proximity motion detection. I’m placing one on the ceiling just inside the bathroom
These are small and cheap enough that I could take one apart and use just the circuit board, soldered to wired power to. wake a sleeping LCD dashboard display.
Certainly worth the $5.76 I paid
Next, I will experiment and move these around the house to see how they play with an existing Zigbee network
Here is a short video: iCloud Photos - Apple iCloud
Link to one of many sellers
https://www.aliexpress.us/item/3256809943593621.html
I will do a real review later, after I’ve used it for a few weeks