Android already natively has a similar feature (at least in the last versions, not sure about kitkat and lower). So how does this app improve on that ?
The app I have developed aims to go further. First, its availability on the lock screen is clear. You don't have to look for a tiny icon on top left/right side. Besides, it allows to create multiple profiles, which is useful if you have for instance young children.
For each profile, you can specify, emergency contacts but also the blood type of the person, its/her height, weight, allergies, medical conditions and any other information you may consider vital.
In addition, the app provides some utilities that allow to display your location (address, GPS coordinates, altitude), find nearby hospitals, send an SMS alert (e.g. if you are not able to speak in case of emergency).