Mini Thermometer

I went with a small digital used for industrial and food prep stuff. They have hi/lo features and are much more accurate. All the keychains types I have looked at were more decorative toys than useful. The pen style rigs where the readout is parallel to the probe are compact.

I picked this one out just for a quick example:
http://www.cutleryandmore.com/details.asp?SKU=12045

The food therms have auto shut off so your max/min is useless unless you stay up 24/7 hitting the button every 10 mins.

For electronic thermometers, check the specs.: most are only +5/-4 deg. F (or something like that), and in my experience, this accuracy is over a narrow range (+45 ~ +85 deg. F), then varies widely (non-linearly) beyond this range. So at true 13F, a selection of thermometers could read anything from 10F to 18F (for example).

High-end thermometers (like the Kestrels) have better accuracy over the range, but still are +/- 1.8 F.

The one that I have that works the fastest, displays the most accurately (witnessed) over a range of 10 F to 95 F, is a simple Suunto Comet compass/thermo. Sometimes hard to read, but can resolve to 2.5 F increments (each marked increment is 5 F), and is always spot-on compared to "actual" temps. I try to mount it away from my face, as breath and body heat can affect the reading esp. in cold weather.