友里蹤跡 is an iPhone application developed by The Hong Kong University of Science and Technology. It falls under the category of Education & Reference, specifically in the field of Medicine. This app is designed to assist in locating individuals with mental disabilities who have gone missing, but it is limited to the Hong Kong region.

The main purpose of this app is to provide a platform where family members and caregivers can register the information of individuals with mental disabilities who are at risk of going missing. In case of a missing person, they can report it through the app, with the hope of locating the missing individual as quickly as possible.

With the "走失報告" feature, all the information of missing individuals is centralized, making it convenient for "尋跡天使" (search angels) to assist in locating them.

Furthermore, the app encourages everyone to become a "尋跡天使" and contribute to finding missing individuals. By fostering a sense of community and mutual support, the goal is to reunite the missing individuals with their families and create a caring and friendly society.