I have a Coghlan's Digital Dangler, a small, inexpensive device that indicates day, date, time, temperature (and records minimum and maximum temp) and also has an alarm. 1.1oz. including the lanyard that comes with it.

I thought I'd mention it, in case anyone else might be interested. They're discontinued, but there are still some available here and there on the net under $15. I bought mine many years ago, probably at REI, and it's still working.

It has its limitations, of course. The thermometer doesn't react very quickly, and it's not waterproof, but it works fairly well. I think it's fairly accurate, since indoors it agrees with a liquid-filled thermometer I also have.

I recently used it on those hot days we had recently. I went walking on both of the hottest days (I tolerate the heat pretty well), and it recorded 110.8 on one day and 111.7 on the next, riding in the semi-shade of a mesh pocket of my daypack.

Incidentally, something I learned from my little adventure is that lightweight long pants may be a better choice in that kind of heat. I was fine in the shade, but out in the direct sun, I was getting the standing-too-close-to-the-fireplace sensation on my legs.