Sorry for the delay, I completely missed your reply!
Did you try other batteries as well? I just changed batteries, after 8 months of use, it was still working, but I changed it just to be safe. I use the official Home Assistant Companion App for GPS presence detection. I also use it for other things such as notifications and some controls for the home. If you build a nice interface like this one (which I use as well and my wife loves it), I’m sure your husband will give it a try.