I like the idea of a digital thermometer with a remote probe. I bought one from Home Depot that worked ok... for a day. Deciding I didn't want to deal with cheap stuff, I bought this one instead:
Traceable Mini Thermometer - Home Beer Brewing - Mfg# 4039
Certified to be within +-1 degree Celsius over the temperature band of interest, and it even comes with a certificate to show the actual error! (Mine reads -0.5C below true temps). A little pricier than a regular thermomenter, but it works well. Just don't put it in the oven! (I put the probe in there for a few minutes, to see how accurate my oven was, and the plastic sheath started wrinkling up! Fortunately the thermometer still works fine). They sell another model that is certified to be within +-0.2C (I believe) but that is more expensive, and just overkill IMHO.