Though it's not USB (it's serial), I've used the Weatherduck for a while now. It's meant for server rooms, but works great in a growroom!
IT WatchDogs, Inc. Home of the Weather Duck and Power Egg
Not only will it monitor temp and humidity, but also light levels and sound levels. Also allow up to 3 other inputs (soil / res temp or moisture for example, or a door switch).
It's got a web interface and can send email alerts for any parameter - like the soil's dry, or on the security side - a doors been opened. Emails can be sent to your mobile phone as well.
The monitoring software makes nice graphs over time, can log into a spreadsheet and can input a webcam. Again that can be triggered, like when the door opens it snaps a photo. Or evertime the lights come on (could make a nice time-lapse...)
Grow on
