Measures against overheating / Was: static or dynamic /dev
although there isn't really anything left to add to Bobs reply (which is good work, as expected); but just for the fun of it, some related ideas.
If you need to monitor harddrive temperature, then possibly you've already reason to fear overheating, and you finally would need to lower the temperature generally, right.
There are settings in the BIOS as well as in the desktop settings what to do after so much idle time (or tools like 'sleepd', or you could screw some hdparm -f -Y command into the right places.) However, that does not really work since there are too many processes doing continuous small disk writes, like logs and network activities. Therefore, you should configure as much things as possible into RAM (see /etc/default/tmpfs) and even link specific folders there. As a small demonstration, some image viewers clutter your disk with large amounts of thumbnails in ~/.thumbnails, and you could make that a symbolic link to a /tmp/thumbnails folder which you create at desktop launch, via autostart script. (I invented this just now, not tested.) The thumbs will be lost, after shutdown, but usually most of them are obsolete anyway. Highly experimental would be /var/log mounted as tmpfs :) but why not.
However, if you've got serious overheating, then the real solution is to get the heat out of the computer. With PCs for example i tend to use external drives for the busy system partitions. In very modern laptops you would have an internal flash disk anyway, which probably don't produce much heat. But a simple thing you can do is to clean the inbuilt fan from heavy dust and you may even consider to open up some additional slots in the case, manually, or make the existing one larger (loosing warranty of course).