If you are getting a table top incubator like a Hova or LG, they do not come with a humidity gauge you have to get one of those separate. Most do not come with a Thermometer. Like a Temp/hygrometer. Springfields, Accurite, Bemis to name acouple.
Also, you will want to calibrate your hygrometer to know how accurate it is.
Here's an excellent site that walks you through it. http://exoticpets.about.com/od/herpresources/ss/hygrometer.htm
Folks will tell you there favorite brand and type. So, you will get more ideas on which brand.
I have a Radio Shack thermometer/hygrometer and it tested pretty accurate. 2% low