I'm thinking about putting a "Smart Mirror" in my bathroom. I was originally going to use a Raspberry Pi mounted in a waterproof box near the mirror. If it's feasible, I think I'd rather run some CAT6 to it, and use a device that's already in the server rack.

Is there a reliable means of sending video signal over Ethernet for distances of 70ish feet?

I could use a long HDMI cable, but the idea of having the CAT6 in the wall in the bathroom is appealing in case I ever want to re-purpose it.

You can do it with HDBaseT

I've done it a few times with these

https://www.orei.com/products/ex230uhd-hdbaset-hdmi-extender-230feet

I've used something like this.

https://www.monoprice.com/product?p_id=43959