DC Rainmaker has done a lot of drone reviews. https://www.dcrainmaker.com/product-review-types/drones

I use to be interested in getting one that could follow me. However those places I'd want it following are also places where drone use is not permitted or very limited. Such as going up Mt. Bluesky. I don't think they are allowed on Pikes Peak either.

My son has a drone, but not with following capability. He has on occasion snuck up on me with it when I'm riding solo and gotten some shots. Once I heard the noise, but thought is was a group that I'd just passed catching up. You could see that I sped up and climbed the next hill like a bat out of h e double toothpicks.