I believe the zilla only reads one temperature. The acu-rite that everyone recommends on here reads 2 temps (one at the unit and one on a probe) as well as the humidity at the unit.

EDIT: The one in the link above is NOT the one that gets recommended around here a lot. Here is a link to a pic and description of it. You can probably find a better price elsewhere, that was just what popped up when I googled it. In this pic, it is in "clock" mode, which shoes time & temp & humidity. For our uses, the other mode, which shows 2 temps as well as humidity, is better.
http://www.partshelf.com/acu00891.html