That's a good question. It would be worth making a list.
To the best of my knowledge, most of the big brands do not have this, or at least they do not publicize it.
IPVMU Certified | 02/15/16 04:19pm
When you install Dahua's gDMSS/iDMSS mobile app, it comes pre-configured with a demo NVR, I assume at some Dahua office somewhere. (Of course, right now when I want to do a screenshot, my gDMSS app isn't loading ANY of the sites I have configured...)
I once googled the model number of an IQEye camera (looking for information on it), as it displays in the camera's web interface... and got dozens of hits of active, unsecured cameras from around the world... kind of unofficial demo? ;)
IPVMU Certified | 02/15/16 04:38pm
Video Insight does, demovi.com Although they don't manufacture their own cameras. Panasonic and Hikvision rebrand.
We have a site in Montana we provide credentials to known dealers. It has a variety of cameras, but certainly not all.
IPVMU Certified | 02/15/16 05:38pm
If you download Exacq VMS software it has huge selection of cameras to choose from. I have used it a couple of times for clients.
Avigilon has a demo NVR that streams from several locations. It's not an all-encompassing selection of their cameras, but it gives you a good idea of the capabilities.
They also have one to demo the mobile application.
Ask and ye shall receive, John :)