+1 on wired cams. I put in cameras for neighbors that use them for calving barns or monitoring pens, and I would never use wireless, even though there's no interference sources when you're 2 miles from the nearest neighbor. It's just so much more reliable. That's where I've used POE switches and injectors, but I've never encountered a version that sits inline for pigtailing off the power leads, but I guess I should have predicted that they'd exist.
Cheers!