Sure wish my dogs chased things like that, it would be a cool way to give them a work out. My dogs don't do toys nor do they fetch...way beneath their dignity.
Now, you put a cat on the other end of that line and Ben will run all day long...though if the cat were Flash he would likely lie down and bump his face on Ben's nose, wanting love instead.
I like that now! And cheap to put together. Definitely cheaper than replacing shredded furniture or carpet. I sure could have used a treadmill or a giant hamster wheel when my girl was young. I did have a lot more time to walk her back then and put a doggie backpack on her with a couple water bottles for weight. We used to do a lot of mountain hikes too.