This paper deals with the localization module extension for various platform to support locating in the interior. Any mobile devices (vehicles) can be equipped with a GPS module for location, but in areas with high density in the building interior or city centers a location using GPS is not suitable due to insufficient signal. The solution for these sites can be seen in use of existing WiFi infrastructure. The result of described paper is software module for mobile device. This localization module communicates with the WiFi module for position evaluation of mobile device based on maps and signal strengths of visible WiFi APs.