I don't know exactly what an app is, but apparently I've never needed one to operate my LabRadar for the last 7 or 8 years or so. I don't recall it moving around and I use it regularly.
I have one of the early LabRadars that does not have BlueTooth so no way to use a phone anyway.
The onboard SD card performs the function of data collection and transfer to your computer for further analysis.
The unit is big and heavy enough I also have not had problems with it moving once set up.
The main pain is remembering to reset the triggering if it times out.
Dunno how many shots I have missed because the transmitter timed out to save battery.
Yeah there is a setting for that but like I said above, I am slow.

If I was still shooting the way I was 10 years ago and had the money I'd definitely get a Garmin but for now I'll just have to be envious.
Anyone tried chronographing a shotgun with the Garmin yet?
That's one of the trickiest situations.
The magnetospeed will do it if you futz with the settings all the way sensitive.
Sometimes.
Never willing to brave aiming a shotgun at an optical chrono and I never tried with the LabRadar
just guessing the return signal, what there was of it, would be a mess.