The biggest problem I've had in the past with digital thermometers is preventing them from being damaged by moisture.

I've had the best success with the models that have a probe on the end of a cord. Here is an example of something similar:

http://www.digitalthermometers.net/d...antrwt800.aspx

If I were to work in a shared darkroom, just for fun, I'd like to use this one :

http://www.digitalthermometers.net/b...ermometer.aspx