I have recently purchased a USB dongle to measure temperature and humidity. This dongle is supported under Linux as follows: 1130:660c Tenx Technology, Inc., I am quite happy to see that a few projects exist around this device. I have found one which seems to work properly. You just need to compile it then it will give you the following on first run:

./temper
Found device: 413c:2106
Found device: 046d:c00e
Found device: 1d6b:0001
Found device: 067b:2303
Found device: 1d6b:0001
Found device: 1d6b:0001
Found device: 1d6b:0001
Found device: 1130:660c
Found deviceNum 0
Trying to detach kernel driver
detach successful
detach successful
sending bytes 10, 11, 12, 13, 0, 0, 2, 0
sending bytes 82, 0, 0, 0, 0, 0, 0, 0
sending bytes 10, 11, 12, 13, 0, 0, 1, 0
Other Stuff (232 bytes):
57 58 14 00 14 00 53 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00
sending bytes 10, 11, 12, 13, 0, 0, 2, 0
sending bytes 84, 0, 0, 0, 0, 0, 0, 0
sending bytes 0, 0, 0, 0, 0, 0, 0, 0
sending bytes 0, 0, 0, 0, 0, 0, 0, 0
sending bytes 0, 0, 0, 0, 0, 0, 0, 0
sending bytes 0, 0, 0, 0, 0, 0, 0, 0
sending bytes 0, 0, 0, 0, 0, 0, 0, 0
sending bytes 0, 0, 0, 0, 0, 0, 0, 0
sending bytes 0, 0, 0, 0, 0, 0, 0, 0
sending bytes 10, 11, 12, 13, 0, 0, 1, 0
temperature 75.20F 24.00C

Note the temperature on the last line. Since this is a C file, you just need to tweak it according to your needs. You can also download a perl class if you prefer. And last but not least, it is also possible to add it to cacti