After reading Steve_M's post it struck me perhaps Stone was asking about the HM in general, and not just the board (which is what this thread is about)
The Heater Meter is pretty much like you described, an internet controlled "BBQ Guru", except IMHO the HM is WAY better than any of the commercial BBQ controllers available out there. The basic concept is, the HM board controls a blower and/or servo damper which will regulate the air flow in a grill/pit to achieve the desired temperature. It can read the temperature of 4 probes, one of them is the pit probe that is used to control the temp, the rest can be used in foods. There are too many other features/options to go into in a brief description, but that is is basics of it...
As for getting one, it's like Steve said, kinda like a modern day HeathKit, but not quite as spoon fed (but almost). Bryan designed the thing, puts up the WIKI guide which includes the build instructions and parts list, with a clickable BOM that will load all the parts you need to build the unit into Mouser and Digikey shopping carts (these are electronic parts supply companies). Then you need to acquire a HM circuit board (explained above) and build the HM board yourself. This unit can work in a stand alone fashion (not network connected), or you can add a Raspberry Pi mini computer board to it and that gives you the web interface with all the bells and whistles. At that point you have bare bones circuit boards, you can use them as is (though its a bit of a PITA to use the bare circuit boards) or fashion up your own case, or order a neat 3D printed case for the unit which Matt and Tom in the forum have developed. At that point you've really got something!