What clocking has to prove
Three things: that it was this guard, that they were at this site, and that it was at this time. Hardware answers the second and third. A phone can answer all three, because it can also take a photo.
How a phone proves presence
- Position. The phone's location is compared with the site: a circle around a pin, or the site's own area drawn on a map for a large property.
- Time. The phone's clock is checked against the server's, so changing the phone's time does not move a book-on.
- A photo. A selfie and a photo of the post show who is standing there.
What makes it trustworthy
A clocking app is only as good as what it refuses. These are the rules Truepost applies to a guard's own book-on, book-off and site report.
- Location must be switched on. No position, no book-on.
- The position must be fresh. A position from ten minutes ago is where the guard was, not where they are.
- Fake-location apps are refused.
- It must be inside the site's line, with a small allowance for the phone's own inaccuracy.
- It must be the guard's own posting, and not hours before the shift.
When a rule refuses a book-on the phone says why, in words, and tells the guard to phone the office. The office can always book a guard on itself, and the record says that it did.
Where a phone has limits
- Indoors and in basements a phone's position can be rough. A QR code at the guardhouse, scanned to book on, is a useful second proof there.
- Not every guard has a smartphone. A shared phone at the guardhouse covers a site.
- A phone proves presence at the site, not a walk past each checkpoint. If your contract requires checkpoint-by-checkpoint patrol rounds, you may still need tags for that part.
What it costs
No readers to buy, install and replace, and no visit to a site to fetch the data. The costs that remain are the software and the data the phones use, which for an app built for entry-level phones is small.
See the Truepost guard clocking app
Written by the Truepost team at Sentrio Systems. Last updated 10 November 2026.