As we know, regular walking has been recognized as an effective method to reduce the risk of chronic illness. However, for some elderly people, due to the gradual degradation of their cognitive function, a regular walk might become a missing-person occurrence. This study therefore establishes a customized safety area as the second feature to assist this group of people. Normally, the safety region, such as a nearby park, grocery stores, library, bank, or some shops, can be deemed as familiar locations for an elderly individual and can be set as a safety zone. Inside this area, the system will not issue any alert alarm. The GPS coordinates, i.e., the longitude and latitude, of such neighborhood features as are listed above can be set up by inputting those data directly if the user has this information or by using the PTFaD to read the GPS coordinates. Also, to make this system operate smoothly, when the system is started up, the smartphone is able to automatically turn on its Bluetooth and WiFi functions to increase the accuracy of positioning. In the present study, the first layer of the safety zone is set to within a radius of 300 meters. That distance is considered a safe area for the elderly (see Figure 4). The second layer of the safety zone is set to within a radius of 500 meters. If the elderly individual stays between 300 meters and 500 meters, the system will trigger the alert function. The alert system first broadcasts pre-recorded voice files by the elderly individual’s family to request the elderly individual not to go too far and to ask that elderly individual to go home soon. The voice messages should be something like, “You are too far away from home; please come back as soon as possible.” For those people in early stages of dementia, that message plausibly makes sense. For people in later stages of dementia, although they may have lost the ability to go home by themselves, those pre-recorded voice messages provide opportunities for bystanders or police to better understand what that elderly individual needs.