If it's a Windows-base DVR, you can install the UPS software that will monitor the UPS status and initiate a proper shutdown automatically when the power gets low.
The idea was a standalone Linux based DVR, running without monitor. There will be power outages, and they will drain the battery completely and there will be noone around to reset it. So .. I'll be wanting somehting with BIOS wake ... wake-on-lan or something.
I'm fairly handy with Linux, so as long as it will wake up and connect to the internet I am happy entering the system myself by SSH and fixing anything by hand. So either wake-on-lan or some BIOS setting. Though maybe I might have to build a system myself rather than buy a standalone (later I'll maybe ask you all for opinions on the models available here to see if you have experiences)
Cheers