LocationTeller is an Android application that was created to support still mobile people suffering from dementia, and their relatives. The main functionality is to send updates about the current location to a server periodically. The locations can then be displayed on a map view.

So when a disoriented person goes out for a walk, he or she can take a smart phone running this application. Other people can track the current position of this person.

There are many applications available that support tracking of the current location. For the intended use case the tracking requirements are a bit special though. Rather than being highly accurate, it is more important that the app is always active, saves energy, and sends location information in a reliable manner. People suffering from dementia might leave their houses at any time without telling their relatives. So a typical usage scenario could be that the smart phone is put into a pocket of the clothing of the demented person. When he or she is gone it is then possible to query the current position. For this to work the application must be running continuously without draining the phone's battery.

To make this possible, the tracking behavior can be configured with different parameters:

• The tracking interval: This is the interval in which location updates are sent. It is specified in minutes because for the intended use case this granularity is sufficient. (You do not need to know the exact position in real time; it is enough if you know where the person was a few minutes ago.)
• If a location request yields the same position than the previous request, the application assumes that tracking is in inactive state. This means that the person is no longer walking around. The application then switches in a stand-by mode by successively increasing the tracking interval by a specific value.
• The maximum tracking interval: If this value is reached, the interval between two location requests is no longer increased. The application stays at this interval until a change in the location is detected again. Then it switches back to the tracking interval.

By fine-tuning these parameters, the tracking behavior can be customized to your own specific needs. The greater the maximum tracking interval, the less energy is consumed by the application when it is inactive - but the longer it takes to become active again and send an up-to-date location. So these parameters have to be balanced carefully.

Another difference between LocationTeller and typical tracking applications lies in the fact that locations retrieved are directly uploaded to a server, from where they can be accessed by the receiver part of the application. Other tracking applications usually record a complete track which can then be exported manually.

The server to which locations are uploaded can be configured. Currently servers offering the WebDav protocol with basic authentication are supported.