Can any other fitness trackers work with the Apple Fitness App?

I love my Apple Watch, and I love the Fitness App. Closing all my rings has gotten to be an obsession (but a healthy one). Sometimes though, I don't want to use my Apple Watch. When I'm dressed up and going to a smart event, I like to wear something a little blingier - but I don't want to lose those precious move hours. I'd like my movement to be tracked, even if not so precisely as my Apple Watch might do it. So, are there any discrete, screenless, bracelets or straps that I can wear with my dress watch that will track my movement and add it to the Fitness app? And, if there aren't, I'd just like to say that I'd love to see an Apple Fitness Tracker - just a band, nothing more, that performed that function!