Any recommendations on simple trailer camera? 
TIA! 

For backing up? Or to see in the trailer while driving? 

I can't really help you with a back up camera. (Maybe check out Amazon)

But if you want a camera to check on the horses I have used a baby cam before. Lots cheaper and easy to set up. 

I tried the baby monitor route first... it was alright but was really zoomed in and the battery only lasted like 3 hours. I recently purchased a wireless camera system off of Amazon. I am hoping to get it installed this week. 

Yes, Horse area- baby camera is a great option and one could probably be found reasonable on eBay- thank you! 

Panamas gold- thank you! 
woukd you share which one you purchased on Amazon? And keep us updated how it works! I have a poor hauler who's constantly kicking a thrashing around- despite kick chains and hobbles- want to see what is going on back there. 
thank you! 

This is like the one I purchased... camera needs to be connected to running light for power... connects to monitor wirelessly and no wifi needed.

https://www.amazon.com/Emmako-Wireless-Waterproof-Distortion-Reversing/dp/B078PDH6Z8/ref=sr_1_1_sspa?crid=1FGSKGZRTRS4E&dchild=1&keywords=amtifo+a7+hd+1080p+digital+wireless+backup+camera&qid=1627492323&sprefix=amtifo%2Caps%2C824&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzME80VThEUDRCVE80JmVuY3J5cHRlZElkPUEwMjI1MTU0M1NNVVVKNVhYMFA4MiZlbmNyeXB0ZWRBZElkPUEwNzE0MjgzMTNaMVVPQUNFQUtSRCZ3aWRnZXROYW1lPXNwX2F0ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=

Have you had a chance to try it yet?  I too went the baby monitor first, not knowing it was only good for about 3 hours (which does NO good on long hauls).  So this one looks pretty cool & wondering how you are liking it.

and was it all complete or did you have to order the extra stuff that pops up with it when you put in the cart?

Yes, I have used it and I LOVE it!!!! I am going to add another camera in the horse area... the camera angle shows two stalls really well and sometimes I have a full trailer. I'm going to put one on the first two stalls and move the current camera back to the last two stalls. I am going to attempt to attach a picture...