As part of the digital humanities project DARIAH-DE a very useful and user-friendly georeferencing mobile app has been programmed and developed since 2014 by Harald Lordick (Salomon Ludwig Steinheim Institute for German-Jewish History):
The app locates the user and provides him with the locations of objects, buildings, institutions, places and events of historical importance for the German-Jewish community. The coordinates are delivered by data from Wikipedia and other sources. The data sets contain, if existent, links to the related Wikipedia articles, enabling the user to obtain more information and also imagery on the respective locations; due to lacking uniformity in the licensing models it is not possible to implement content from Wikimedia Commons into the app.1 Hosting and geoservice are provided by the infrastructure of DARIAH.
For more information see also the (German) weblog of the developer: https://djgd.hypotheses.org
A screenshot (using a desktop computer) showing the locations of the “stumpling blocks” (“Stolpersteine”, commemorative plaques for the victims of the National Socialist Regime) and the Old Synagogue in Regensburg.