I'd like to know what the temperature is in a small server room (three full size racks, one L shaped desk, lots of shelves all around) .

I could buy some random thermomethers, and stick them to walls / and racks, but I would really like something that sends out an email when a threshold is met.

But, really, nothing more than that.
Is there something that can be connected via USB to a PC? Or maybe a network devices, wired or wireless, that can serve this purpose? Or, any other relatively inexpensive solution anybody would recommend?

Thank you!