meteohub.de

Can you explain the " sniff weather data" feature? What exactly does it do? I see it can be used with the Acurite Internet-Bridge and the Ambient Weather ObseverIP Module. Does it capture the data being uploaded to Wunderground?

Observer-IP has a web interface where Meteobridge can read data from.
Aculink does not have this, so it needs a setup where Aculink connects
to the Internet through the Meteobridge. Passing the traffic through
the Meteobridge allows to "sniff" the data and to make use of it with
the Meteobridge.

Can you say just what is "sniffed"? is it the wunderground uploads? Will it capture any device uploading to wunderground as long as the packets pass through the MB?

Not the optional WU upload is sniffed, but the data transferred to the Aculink network.