EMT's and Paramedics are taught to look for Medic-Alert bracelets and necklaces, so you need it in one place or the other or they may not find it in time. The necklace usually comes with a ball-chain like military dog tags- that will clue them into it's purpose even if it's tucked into your shirt. It will come apart easily enough should it get caught in moving equipment. You may get a skin lesion should that happen, but you survived and that matters more!
If your condition is such that you may not be able to communicate your medical problem should you get hurt, then limit your shop times to when someone can help keep an eye on you just in case the worst happens and be sure they also know what to do for you till help arrives.