I would go with a cheap, lab grade, analog thermometer, like http://www.midwestsupplies.com/12-laboratory-thermometer.html.
Remember that accuracy is important, but consistency is VERY important. These thermometers are more then accurate enough, but they are very consistent. Even if they are off by -.5 degree (which would be extreme) that particular thermometer will ALWAYS be off that much.
I'm not sure what you are saying, as a device cannot be accurate without being consistent (aka, precise), except for random chance. I think you are saying that these lab thermometers are precise, but not necessarily accurate, which would be the case if it read consistently -.5F off. I agree with that.
That said, it's easy enough to validate it in an ice bath and in boiling water, and to compensate if need be. I have used these as well as both cheap and expensive digital thermometers, and I find the analogs to be more precise (even compared to the expensive thermopen). These are also inexpensive enough to buy a pair or more, and if they agree they are highly likely to be accurate.
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