FindMe Everywhere!

This app allows people who have it installed to find each other no matter how far apart they are.
If you're lost and someone else, who you have in your contacts, has the app installed, you can contact them though it and the app will send your location to them. No one else but them will receive this information.
Likewise, if someone who has you as a contact, and has this app, is lost, they can contact you through the application and you will receive their coordinates at the moment.

Also, you can switch between routes to different people that have contacted you about their location and search for each individually while keeping tabs on where other people are located.

The app can be used in many varying situations - from people lost in the mountains or the deep woods, or in an unknown territory or city, or country with foreign languages, to the most mundane of situations such as being lost in the city or even in a large parking lot.

The mechanics of the app are simple and easy enough for anyone to use, regardless of age or experience with a smartphone. Coordinates are sent through sms and so may cause some additional charge.