Oregon Scientific makes many models of Temperature and Humidity sensors both under their own name and OEM'ed for other companies like radio shack. Though there is no guarantee if the case and options are the same as any of these units it will likely work. These are the model numbers of devices I know for certain to work:
THN122 outdoor unit, no display, -22 to 140 range. Replaced by the THN132
THN132 outdoor unit, no display, -22 to 140 range. Replaces the THN122
THR138 indoor only, temp only, display, -4 to 140 range
THC268 for measuring water temp for hot tubs etc. display, has 10 foot wired probe. 4 to 140 range
THGR268 temp and humidity, display, -22 to 140 range, humidity 2% to 98%
THGN123N outdoor ultra cold temp and humidity, -40 to 140, no display
THGR810 10 unit module, temp and humidity, display, indoor, -22 to 140
THGN801 temp and humidity, no display, for weather stations, large and mounts on wall
THWR800 floating water temp module, display
RTGR328NA temp, humidity, clock, display, indoor, -4 to 140
RGTR328
AW131 high temperature meat thermometer. This is a nice unit and has a range from 32 to 500F. Problem is that it shuts off after 8 hours. I tried to use it to control solar hot water pump but the shutting down after 8 hours was a deal killer.
If you have a device that has multiple readings remember to create a Unit in XTension for each reading of the device on the same address. So for a humidity/temperature device create 2 units with the device type set to the appropriate sensor input but the same address.