I really am not trying to pick on anybody or piss anybody off, but I am wondering how much this really matters. If you use the same equipment, even if it is off the standard somewhat, you will get consistent results and so you can keep good records based on readings from the same tools.
Lets face it, there are so many variables in this game that focusing on something like calibration of a thermometer seems to me to be a wild goose chase. I mean, for example, do you check and adjust your ph everytime, read your malt analysis sheets, chart hop age and storage, map your temperature fluctuations during fermentation, and so forth.
My point is simply not to worry too much or spend money on things with the idea that they will be the silver bullet for making great beer everytime. I believe that consistency is key, and a $2 dairy thermo can give you that. IMHO.