I love this idea! I wanted something like this for kiteboarding, actually, which an interesting coincidence given the name.
Some UX feedback: You should warn the user in advance that you are going to send an SMS to their phone number to confirm the number. After getting the first SMS to confirm my account, I started to add my emergency contact. I stopped, though, because I was worried that you might send an SMS to them asking to confirm their number, status as emergency contact, etc. The UI doesn't make it clear what will happen when I add them as a contact.
Some UX feedback: You should warn the user in advance that you are going to send an SMS to their phone number to confirm the number. After getting the first SMS to confirm my account, I started to add my emergency contact. I stopped, though, because I was worried that you might send an SMS to them asking to confirm their number, status as emergency contact, etc. The UI doesn't make it clear what will happen when I add them as a contact.