Just thought I'd share a project I'm working on for a cheap remote camera system. The range is short but it connects to a cell phone without needing to download an app. Max range line of sight is currently 300 feet to me Iphone 6. I'll be adding a project later that has a boosting repeater.
It's based on the ESP32-Cam for about $15 Canadian. Plus some power supply parts and 18650 batteries. Total cost to build this was under $30.
With the short range it limits the uses for this, but though I'd share it anyway just incase it works for someone. They're great for monitoring camera traps from a distance as well as animal traps to limit the amount of time the animal is in the cage.