Welcome to the forum cokeman.
If she want to watch him literally, that will narrow down the field as very few LTE cameras have a interior camera, if she just want to monitor his driving no problem.
This is going to cost her, a constant video feed running over a LTE connection, and the old guy driving that much every day, that will probably necessitate a flat rate data plan for the SIM card.
Also if the old guy is driving out into the countryside, chance are you will not have good enough 4G coverage to have a constant connection, even in little old pretty much flat Denmark, and you usually getting 2 service providers due to them sharing networks, well you can still find dead Zones,,,,,, very small ones here of course.
Also these LTE / cloud systems, also the most expensive ones out there, so just getting the system your mother will have to cough up a substantial investment.
Both on 4G and 5G we Danes have,,,,,, well at least 4 nationwide providers. i am with the #2 largest one, that have roaming agreement with the #1 one.
I am not much into the smarts of phones as i dislike them very much personally, but with a smart phone, and say a health monitor paired to that, couldent your mother keep track of him too that way, also location i would assume.
I know parents can track their kids with a app / function on phones.
Assuming the old guy have a smart phone, that could be a cheaper route than a LTE dashcam which your mother couldent watch all the time anyway.
Lost my own dad a month ago, but due to quite normal things, the old guy did get a driving licence in the 80ties, but i dont think he ever used it.
The tracker nizmos mention also a good / cheaper option.
PS: Tell your mom a elderly Danish guy send her a virtual hug, for caring so much.