Here’s one for the travellers.
Maps.me is a free app that allows you to download maps when on WiFi and then use them whilst you’re travelling around somewhere where you don’t have data.
In my experience (at least with an iPhone) you can use GPS to track your location even if you don’t have any data for the country you’re in. So you download the map and then track yourself on it.
You can download maps for offline use on Google Maps… but it all feels a little easier on maps.me.