A drone fence. Hear me out.
Problem: Fencing is FUCKING expensive. For many people who want to keep animals out (garden, animals pooping in the sandbox) buying a fence is really cost prohibitive. Plus they don't always work anyways.
Solution: Self driving drones with IR cameras in specific locations. Place a camera or two in strategic locations, and have a drone take off and chase off deer or rabbits. Return to the main station, land, recharge, repeat. Might need to have a squirt gun with some vinegar or something to scare off the more aggressive deer.
But combine some machine vision (don't want to chase children), autonomous flying drones, and some smarts, and you could have a $2000 system that replaces a $X0,000 fence.
Sorta the opposite of an invisible fence for animals.
I would LOVE one of these. I just don't have the capital or talent to make it happen...