The other use case can be in sport area. Like paragliding where the participants should be tracked and scored. The location should be tracked every 3 second and send to the server when network is available and it is better to be send LIFO (last in first out) so the server knows the last location as soon as possible to show it to the spectators on the web site. Also the server must care about, the rules (where to go and where not to go), the safety (where was the pilot lately if she/he is missing) and at the end of competition to collect them from about 60 km wide playing field with designated vehicles, the server must track the vehicles as well. One more thing, the altitude is also important, not only lat/long.
The spec might be like to register to get the location every 3 seconds / every 10 meter, and the user get a permission box to allow or not. And the service worker get a location changed event every 3 seconds / every 10 meter.