I'm liking this thermometer which I got from Amazon.co.uk, but I can't see it available on Amazon.com -
max min digital thermometer - with in out sensor & high low alarm - ideal for greenhouses & grow rooms: Amazon.co.uk: Kitchen & Home

The temps are accurate to within 1C on both probes (external probe is slightly better from my calibration tests). The thing I like most about the unit is that I can set a max and min alarm. I got it when I planned to brumate this winter to monitor brumation temps. It's a great unit if you can find it available.