GTM Commander is a useful tool which should simplify and speed-up the work with the Google Tag Manager (GTM). The tool offers the feature to copy tags, triggers and variables between containers in an easy way. Especially if you work with lots of containers you can save time and speed-up work.
With the POI Assistant app you can use POI files in OV2 (TomTom) format on your Android smartphone in order to find different kinds of POIs in the sourrounding area (i.e. cash machines, gas stations, fast food restaurants, ...).
The Sea Maps app allows you to view the OpenSeaMap nautical information layer on top of Google Maps. You can optionally toggle an option to follow your position or center on your current location.