The original Wattmon is no longer being produced, and is only partially supported. They are still in use by some, I'm sure, but they are no longer available.
Note that most but not all of the uPHP software reference information documented elsewhere in this Wiki applies to the original Wattmon. However, it had much older versions of the firmware and operating system, which were brought into the WattmonPro and improved.
For those of you who might yet be using the Original Wattmon these User Manuals are helpful:1)