That’s my cam lock at work. I’ve enrolled all my NFC implants, and gave the site manager a card to get into my locker just in case.
Just talk to your gym manager, tell them what you want to install and how they’ll be able to get in too. They may well say yes - if only for the novelty of having a cyborg patron. But if you do it sneaky-like, they’ll notice and it won’t fly.