VHF will be better simplex in the mountains than UHF. I'd call the folks making the system and ask how much power the handie and the alarm transmitter runs. I just guessed at 2 watts.. might be 5, or it might be 1. With a stated 2 mile range it won't be much. The alarm transmitter looks like it has a removable antenna, and if so, a better antenna mounted on the roof of your truck will significantly increase the range.
PaulT makes a good point, a ham license is easy to get today, and with that, you can run much more power from the mobile, and of course won't be limited to MUR radios. I presently run an APRS system in my truck which allows anyone looking at a particular website to track the location of my truck as long as it's in range of APRS receive sites.
Slight hijack here: PaulT what's your call?? I'm K6ON. Do a QRZ lookup and you'll see the mobile and APRS system, and also a picture of the old Cessna 210 Centurian I putt around in.
2007 Dodge 2500 5.9 CTD QC 4X4, *1996 FWC/ATC hybrid* *2021.5 GeoPro 19FBS* "If you can read this, Thank a Teacher. Because you read this in English, Thank a Vet."