OSMCache
The web page is a web application that uses OpenLayers to show map data from OpenStreetMap. Location tracking is used and a few simple options are available so that the page can be used for basic Geocaching.
There's also an Android app available that allows continuous tracking of your GPS coordinates, even when your smartphone is locked.
The web site itself can be found at https://j0r1.github.io/osmcache/ and the development page at https://github.com/j0r1/osmcache. The app is available on the play store: QOsmCache