I just went ahead and deleted my previous post. Got a lot of answers from doing and learning as I went along with the help of Jay over at the Indigo forum.
I got the plugin for Indigo and edited it as advised, and am ready to receive a url. Windy I can test this whenever you get WD to post a url. I would suggest a control panel that the user might select the parameters they want to send to Indigo, then the url would be sent based on the user's selections, much like WU or Awekas. But I already have a text file template ready to go that I have been using in the webfile realtime control panel along with testtags, so in that case could just use the http screen instead to process it. Just that a control panel would be so slick in this case.

Regardless, Indigo will automagically create and populate it's internal vars from the data sent.
Here is the url that would need to be sent, along with a sample data feed. Note that this is derived from the present LWS plugin for Indigo and the data is not metric in the url so this would be something you would want to look at:
http://host:port/wd/importData?&date=2009-05-12+17%3A22%3A12&winddir=270&windspeedmph=0.0&windspeedmphav_10m=0.0&windgustmph=0.0&windgustdir=270&windgustmph_10m=0.0&windgustdir_10m=270&humidity=47&dewptf=69.836&tempf=93.200&raininch=0.000&rain24hinch=0.000&baroinch=28.508&action=updateThe url begins with
http://host:port/wd/importData?This would create the following variables in Indigo and populate them via the plugin:
WD_windgustmph
WD_tempf
WD_raininch
WD_windgustmph_10m
WD_windspeedmph
WD_windgustdir_10m
WD_humidity
WD_winddir
WD_date
WD_windspeedmphav_10m
WD_baroinch
WD_dewptf
WD_rain24hinch
WD_windgustdir
Again this is derived from the existing plugin so the data WD includes in the URL with WD's naming convention (as long as it's plain text) will be recognized in Indigo.
Let me know if/when you have something to test and I will give it a whirl!

ArtPic, depending on Windy's feedback, I will make a copy available to you as well... and I think bbruck might be interested in this as well. So 3 of us potentially could test.