Here is a link to a cheap probed thermometer. typically humidity is less than 10% higher in hides so a single ambient hygrometer is all you usually need and if it is kept around 50-60% there should be no problems.

http://cgi.ebay.ca/New-Digital-LCD-T...item415167348c

http://www.amazon.com/Western-Digita.../dp/B0007VWEQA