The WS100x wifi does send data to WU only. The Airbridge provides much more options what to do with your data. It supports rapid fire sending to WU, supports much more weather networks, can upload to your own servers, send email alarms on individual defined conditions, etc. When you are interested in details, give "wiki.meteobridge.com" a try, where all the features of the Meteobridge are explained. The Airbridge is from a technical point of view a Meteobridge on a TL-MR3020 platform with a Meteostick connected, which does the RF reading from the WS100x outdoor sensor unit.