Feed it from the collar
Anything that can make a web request can report a position: the tracker's app, a phone shortcut, a cron on a laptop.
Fields it will take: lat/latitude, lon/lng/longitude, ts/timestamp, acc/accuracy in metres, spd/speed in metres per second, bat/battery as a percentage (or volts, if it is under 5), and note. The key goes in key, or an x-gus-key header.