Here's a project that I just completed: my own version of the upcoming Lionel caboose camera. I use a camera system designed for FPV drones, the Runcam Split 2s.
The neat thing about the Runcam Split is it simultaneously transmits a live tv signal and records HD on an SD card. The live feed isn't HD, but looks pretty good. I watch it with a pair of FPV goggles, so you get live caboose virtual reality! You can see a sample of the recorded video here.
The system is entirely self-contained and track powered. I used a 1F supercapacitor and boost regulator for the power supply. It can sustain the system for 3 or 4 seconds, so momentary interruptions in track power are no problem.
You can configure and control the RunCam over wifi with a dedicated app, although downloading the videos can take quite some time.