Process serving agencies are buzzing around with their GPS apps and feasibility analysis and talking about "proof" and "verification". Some judges are even liking to see this in the courtroom.
I'm pretty up to date on the technology. I wrote one of those apps. In fact, I wrote the app that has market share in New York where all this started.
I wrote it because people wanted it. The truth is that there is no way to verify any of this crap.
To defeat ANY of the apps out there, all you have to do is Google "GPS SPOOFER". You can get one for your iPhone or for your Androids and you can make it think you are anywhere at any time.
Even my app which watermarks the photo on the phone itself is easily fooled by the spoofers.
Go back to trusting your process servers. There are many good ones and a few bad ones just like anything else. It helps a lot to analyse the data, but GPS and photos (which could have been taken by anyone at any time) really shouldn't be held up as "evidence" or "proof".
If you ever called me into a courtroom to attack this "proof", opposing counsel would be laughed out of the courthouse.
Try the spoofers yourself and educate the judges in your area before they educate themselves and wonder why attorneys are introducing crap like that as evidence.
Don't let your competitors rope in your clients with marketing bullshit.