I had no real idea how to phrase it, but all these posts have helped. What I was actually focused on when I posted was mainly hardware that can do what the Arlo cameras do:
- Wifi + battery/solar my house is old and hardwires are a pain in the ass.
- High def, preferably 4k, but 1080 is ok.
- Night vision, color or not doesn't matter
- Motion-activated, and preferably some way to filter out and not trigger on things like passing traffic cars.
- As small a form-factor as possible.
The Reolink hardware mentioned below seems to fit the bill hardware-wise.
I hadn't even really considered the software, as I don't need a lot of features. All I need is to use motion-activated capture to stream to some local storage, and an ability to view a live-stream when I want one. But it looks like there's a lot of options I need to consider.