The AT&T Family Map, T-Mobile FamilyWhere and Verizon Family Locator work as a cellphone tracker that is used to provide the location of family members. Just like Sprint's Family Locator, the services use an app that accesses cellular tower data to determine the location.
For the service to work, parents must enroll their kids' cellphone numbers into the family tracker account. To be tracked, the phone must be turned on and located within the cellular network's coverage area. Some tracking apps, such as the Sprint Family Locator and LogSat Family Tracker, may also use Wi-Fi or GPS signals. Existing mobile phone subscribers can use a free trial before signing up for family locator services, which then typically cost at least $9.99 a month, as of 2015.