This App provides a complete Search and Rescue Watchkeeper services.

Targeted to Autralian Environment initially but designed for world wide use, it is just a matter of loading appropriate data.

It defines sectors is which it operates, these are used as filter fields, so people within a sector can see just data associated with a sector if they so choose, by default they are Aviation, Matritime and Terrestrial. Other sectors can be created.

It key functions are:
Allowing users to define trip descriptions.
Allowing users to notified watch keepers of their trips via either email or SMS messaging.The intent is that the watch keeper will notify authorities to commence reach and rescue when a trip is overdue to arrive at its destination.
Allows users to notify wathkeepers, when trips are successfully completed, to cancel the watch keeper duty.
It provides a notification for overdue trips defined by all the other users. 

So it is not completely dependent on the vigilance of watchkeepers. Watchkeepers can be anyone, but you are potentially entrusting your life to them so choose wisely. Off course other users of the App have access to their contact information, and could contact them independently if they are being negligent with their duties.

It primarily stores data in a public CloudKit database, the user must choose to make data public, before it is seen to all users. The intent is that the data is shared by all Users, but you don't have to share until you are ready.
There is a some private storage used to User specific data, the the Color they have chosen tfor the app background, their google Map API key if they want one. filters they have defined.

It seems that you put now log you devices into the ICloud to get access, you used to be able to get read only access but that is no only possible it seems.

The App is free to all, but after an initial trial period users who create trips will have to pay a small subscription fee.