My wired ethernet triumph was in my current rental. There's an old under-floor evaporative air-conditioning ducted system which is no longer used. I bought a $40 remote control car with large rubber wheels and a low CoG, strapped a GoPro and a head torch to it so I could stream video to a phone, and tied on a piece of string. The mission was to get from my study to the kitchen which is about 10m all up.

It was more of a challenge than expected. The ducting had ramps, multiple corners, debris/rubbish, and a mouse skeleton to navigate around. All of this wasn't helped by the terrible latency and needing to move the phone to different places to reduce distance and attenuation through the floor. I got stuck quite a few times but could always use the string to pull back a bit when I got wedged on a rock. Sometimes I just needed to gun it to get over an obstacle.

In the end, the car and ethernet cable were cheaper than a good wireless card or POE kit, and I got to give away the car to a kid.