I'd just like to add some GIS layers, such as shapefiles in the Maps.me app.
Has someone already done it?
Geographic Information Systems Stack Exchange is a question and answer site for cartographers, geographers and GIS professionals. It only takes a minute to sign up.Sign up to join this community
Not really. The only overlay you can get in Maps.me is the bookmarks (points) via a KML. Convert a shp of points to kml using GDAL or QGIS (if using Open Source tools) and follow the recipe from support page https://support.maps.me/hc/en-us/articles/207895029-How-to-import-bookmarks-
For lines, although I did not see a mention in the doc, you should also open the KML with lines. I was able to see the lines using the same process as the bookmarks tutorial using my own device. For polygons, it does not seem to work.
If you want overlay layers, you may look at Geopaparazzi, another application (a presentation)