Many people keep an emergency contact in their phone, generally labeled as ICE. If you use a passcode for your phone—which you should do—that contact, though, becomes locked underneath your pin code.
Last fall, Apple created a new feature called the "Medical ID" which it keeps hidden in the iOS health app. When I talk with people about their phones, it's often the feature most people have never heard of, but also the one that could save your life.
On your medical ID, you can fill out as much information as you want a medical provider (or a snooping colleague) to know, including allergies and your emergency contacts.
I'm not a medical professional and those who have serious health conditions that generally require a medical bracelet or other identification means probably shouldn't rely on their cell phone to communicate that information.
That being said, filling out your medical ID to at least make your emergency contact accessible without needing to enter a passcode is important. Here's how to do it:
The Medical ID can be accessed from the iPhone's emergency screen. When you're on your lock screen, it's the "Emergency" on the bottom left.
On the emergency screen, you can either place a call or tap the "Medical ID" screen on the bottom left.
This is what the Medical ID looks like. You can fill out your name, birthday, medical notes, and add emergency contacts. Since this information is available from the lock screen, make sure whatever info you fill out you are comfortable sharing. A snooping colleague or anyone who touches your phone can access this. Some people have gone as far as to only put a contact named ICE with their phone number and that's it.
To fill out your medical information, click on the Health app on your phone.
Once in the app, click on the bottom right button to pull up your Medical ID. Your iPhone doesn't know any of this information until you fill it out.
On your medical ID, you can fill out your conditions, allergies, and medications, along with any other notes you have. Again, all of this information can be accessed by anyone with your phone so only share what you're comfortable with.
You can add multiple emergency contacts and fill out their relationship to you. Along with whether or not you are an organ donor, your blood type (if you know it) and your standard measurements.
If you don't want any of this information to be seen from your lock screen, you can hide it from being shown when locked by unchecking this.
You can also delete the information from your ID whenever you need to. While Apple does upload your medical ID to iCloud, it does not include it in your health data or share it with other apps.