Here's a picture of the AcuRite. There are several types, but the rest are wireless. We want that wire so that the unit itself can sit at the cool end while the wire stretches over to the warm end. People have posted difficulty finding it at WalMart. It's over in the HARDWARE section, not gardening, along with other AcuRites and various thermometers.

BTW, that picture also shows various thermostats.