Do open WiFi security cameras exist?

I'm in the market for a home surveillance system. There's just a huge, absolutely stunning amount of competition in this space, but it's really hard to determine what technical features are really available. It seems like the majority of systems are proprietary and upload to a cloud service you'll have to pay for.

I already have a ZoneMinder setup with some old webcams in the house - it'd be great if I could incorporate the new stuff. If not, I'd at least like to have the option of not relying on the cloud and someone else's servers.

So, do "open" WiFi cameras even exist? Even better if they come with a battery option. I'm fine with having the option of using a cloud service, but I'd like to avoid it to the extent possible. Unfortunately, one of the features I really need is push notifications on motion detection, which I suspect is going to really limit my options. What's HN's experience and recommendation in this area? If I do end up having to use a mainstream cloud camera product, what's worked best for you?