This is a wine thermometer. An unnecessary wine accessory, perhaps, but a reminder that temperature is important. Unnecessary, as most wine can be brought to the proper temperature with a little foresight (see below). Important, as the wrong temperature can hide those most desirable aromas and accentuate the bad ones.
Most wine is served at the wrong temperature - restaurants and many wine afficianados make the same errors - red wine too hot, white wine too cold. This drives me crazy. While I cannot certify that I am always at the exact temperature, at the very least I always think about it, and attempt to minimize the frequency and degree of my error.
Based on personal experience and numerous books, the proper serving temperature for wines are as follows:
Red Wines: 'Chambre' is NOT room temperature. Broadly speaking, 16-18 Celsius, 61-65 Fahrenheit, or 289.15-291.15 Kelvin, is the right temperature for a red. I find Pinot Noir better at the low end, and Beaujolais even cooler. You can play around with the range and see what you like, but you will notice this is a fair degree below 'room temperature'.
White Wines: Whites should be 8-10 Celsius, 46-50 Fahrenheit. Inexpensive, uncomplicated white quaffers should be served cooler (or even mixed with ginger ale), while better whites will do nicely at the higher end. Use an insulated bag or an ice bucket to keep the wine from warming up to room temperature.
Note that the glassware and decanters are likely to be at room temperature, so you may wish to err on the cool side as the wine will warm up quickly. Also note the problem of summer weather, which can warm things up even faster.
Of course, it is no good ranting about wine temperature without a few tips about how to get to the right temperature and keep it there. And for those of you thinking "that's great, smarty pants with a temperature controlled cellar", you don't need a cellar.
Room temperature is 21-24 Celsius, 70-75 Fahrenheit. To chill a wine to the proper temperature, the freezer will knock off one degree Celsius every four minutes for a 750mL bottle (a tip from How and Why to Build a Wine Cellar, by Dr. Gold):
So, if you don't have a cellar and keep your wine on the counter, or you just bought it at the store, try this:
Red - chill it in the freezer for 20 minutes
White - the 4 minute rule needs to be modified slightly - about 40-45 minutes in the freezer should work fine
For those of you who don't believe me, compare two bottles of your favourite red - chill one for 20 minutes in the freezer, leaving the other the counter on a warm day.