It records and syncs with your phone , no need to have them in proximity all the time.
There is a QR code for the correct app to install, there are many many apps with the same or very similar names, you need to get the correct one, for all features, some of the others will work but not as well.
Even the one I got from Aliexpress for £3.81 works well enough.
Bought the one you have linked to for my partners neighbour, she is in her mid seventies and likes the option of larger text, to read the time.
The companion app is pretty good as well.