If you want a real fully featured solution, the Home Assistant companion is capable of location tracking and I believe you can send events that push an update, although it may not be accurate. There is also Locate My Device which I’m pretty sure is FOSS and works over SMS, a much lighter solution for your problem but not as convenient with like a Web UI and some such.

All the ones I’ve used require a separate service to actually do the query.
You can use traccar, owntracks, or wanderer (this one is not realtime tho, and requires for you to find an app to send the data).
There’s also gpslogger which can record everything locally (or send it to any URL you set), but you need another app or service to be able to query it properly.

Not sure about the latitude and longitude, but maybe this would meet your needs? http://bubblergps.com/