I'm doing a lot of travel and filming this summer. I am in the Ozarks which are very hot. Is it bad for the camera if I leave it in the case in the trunk sometimes under the hot sun? I have no sense of this.
If you really need to leave it in there, placing the case in a plastic bag and in a cooler with an ice pack may not be a bad idea. Just keep it cool enough to stave off the heat.
And I carried my HMC-40 around in my trunk every day for six months without incident. No special heat-resistant packing, it was in a Tenba messenger bag. I now use a company camera for my video assignments and I keep it in the trunk too. No problems so far.
Heat is one thing, theft is another. I had a custom steel box welded together, and it's bolted to the frame of my car in the back.. Can't access the spare tire easy, have to open the box and remove some bolts, but it's not reefed down hard, just enough to keep the box in place. The odd time I've got my camera with me and I need to stop off somewhere, it's peace of mind. You gotta think, you are a broken window/lock away from losing $4K worth of gear while you are in the store or whatever. Box is big enough for the bare camera, and a small bag of parts. My deductible on damage to the car is $500, which I can manage easily, but the insurance problems for a new camera? Box cost $200 and no common thief is getting into that. It's also out of the sun, so heat isn't really an issue.
Be cautious about putting in some form of cooling, you don't want the camera sitting in a potentially moist area, and you also don't want to move it from a cool area to the outside air so quickly. We don't have to worry about humidity in the tape transport, but there are sill other moving parts in there.
Solid state cameras are better then tape when it comes to heat endurance. I think the odds of your 'cooling' device going wrong is higher then the probability heat will damage the camera...