The Sea Maps app allows you to view the OpenSeaMap layer, which contains nautical information, as an overlay on Google Maps. Optionally, you can center the map on your current location or have it track your current location.
The Navidash app offers a simple point-to-point navigation system based on the smartphone's GPS data, with a display modeled after the ADF and VOR aviation navigation devices. For example, you can use the app for geocaching.
With the HV Calendar app, you can always keep track of the annual general meeting dates and dividends for DAX 30, TecDAX, and MDAX companies. The HV Calendar app also displays the current stock prices and dividend yields for these companies relative to their current stock prices.
The BookCase Android app displays the locations of public book exchange cabinets on a map. Additionally, once you select a cabinet, you can view further details and, if desired, start navigation to the location.