While a camera review may not seem like something gun related I'm posting it because of how much it has improved my shooting and how often people ask me about it.  

https://gunpowdermeditation.com/2017/05/18/gopro-hero-session-review/

I've never thought of using mine for that but damn, I like that. I have the same one only the newer upgraded version. It's pretty awesome.

I've caught a lot of cool stuff on video with it.  From good shots I've made to crazy things like people ND'ing at a match, squibs, etc.  Being able to record my training classes is huge for me.  I took a 3-day course from CSAT called Advanced Individual Tactics, one of the mornings we spent a good amount of time on medical.  No way I can remember everything we went over but I've got it all on video and can reference it at any time.