Devil's advocate stuff:
I'm trying to understand exactly what I need to upload Rapid Fire to WU.
I want to do this without a connected PC.
Note that Weather Plug (and similar devices), as well as WeatherLinkIP, are actually the same as PCs. Single-purpose, no display, etc.
A cheap netbook, or an old-but-serviceable PC (friends, craigslist, etc.) could be a cheaper-better alternative to the Weather Plug.
Having said that, I'll also ask why you
need to upload Rapid Fire? [I understand that it's cool - I'm just curious about why you need to do it]