I have something similar to this but not quite as involved as this one. It's called a Walkydog and it's just a post that sticks out from the side of my bike that has a very short leash on it. The post sticks out far enough that my dog's legs won't get tangled up in the wheels and the leash is on a spring, so he doesn't get yanked around. We have a mutual understanding on how to behave around squirrels and other dogs and he knows I'll ride slow and steady. He's really pretty good with it. I take him with me to go pick up my kids from school and we all ride bikes back home together.
My mom tried one of those with her golden doodle (around 70 pounds, hyper like a poodle and dumb like a golden retriever).
5 minutes in he ran for something, knocked her down (she was in her mid 60s at the time), and dragged her bike away. It had some sort of breakaway plastic coupler too, but it was too pliable and just stretched a bit instead of breaking. Looked like HDPE maybe.
Now the contraption is in my garage, in scrap metal pile. If she wants to ride somewhere with the dog she tires him in a trailer.
