The one company I have heard who specializes in this is SensaVideo. I have never used them and have been told that they only had analog camera versions as of last year.
I've used Winland in the past. They work, no frills, no power required. They don't have standalone wireless sensors, but if you have multiple freezers the EnviroAlert is a good way to go, wired or wireless. It consolidates the sensors to a head unit, which shows status and some do logging via USB or Ethernet (good for medical facilities who need to provide reports on that sort of thing). Then the contacts from the head unit are connected to the camera.
Honeywell TS300, is what you looking for
One of our clients has started using networked temp sensors in their server/IT rooms... they don't integrate with the cameras, but they do send email alerts if the room temp goes outside of spec. PoE-powered as well, so no extra wiring required, just plug it into a PoE switch.
I think a more general solution might be available, but would need more feedback from the professionals in the field, since I'm going on vague recollections.
I think I've noticed digital (CMOS & TTL compatible) inputs on some cameras. For example, I think I've seen Arecont and Mobotix cameras that support this.
A thermostat with a digital output can connect to the camera digital input.
Now the question is, how would you leverage that information which is (presumably) integrated with digital alarms at the VMS? For example, Mobotix has an email notification option you could leverage.
So, the problem is, I tried to open up the product space that could support your need, but I'm too ignorant to provide the details. If you insist on a highly integrated solution exactly matching your needs, it seems like very few products limit your range of choices and prices. If on the other hand the general approach of leveraging camera-integrated digital I/O is workable, you should have a wider range of choices.
Anyone else have more fruitful comments along these lines? ...or if I'm out to lunch, that's good info to know to avoid wasting Robert's time.
I've read more carefully and I see you're way ahead of me, and I'm just repeating info from your post. Sorry for the noise; if I could delete it I would.
I believe Winland has non-powered temp sensors.
Since "has to be pretty" is not on the requirement list: how about a simple freezer thermostat? Here is the most expensive example I could find: Link
This is basically what controls the temperature in every simple fridge, and it should also work on camera inputs.
Thanks all for the feedback. Correct me if I am wrong, it looks like the Winland stuff that is freezer rated requires a Panel and we will then wire the panel in to the digital input of a camera, correct? I am looking for something that does not need a panel if possible.
I think the link provided by Undisclosed (#0323731) Manufacturer might work but I have to check and see if the cameras that we are planning to use supports a dry or a wet contact.