Yep, I have been using Bluetooth headphones at the gym for well over 2 years now. It doesn't matter what size phone you have, they are just so nice to have over corded headphones. I have the Plantronics Backbeat Fit and adore them, especially since they aren't IEMs; as IEMs hurt my ears too much.
If you have an Apple watch and blue tooth headphones you get almost everything you'd need your phone for. You can leave your phone in a bag on a shelf but listen to music, read/reply to texts, pick playlists, time your rest etc. You could even take an emergency phone call. I am so done with wearing my phone on my arm.