To use WeatherBridge or MeteoBridge you still need the ObserverIP that comes with the WS-1400-IP (which I have). MeteoBridge/WeatherBridge gets that data from ObserverIP via WiFi or cable, and ObserverIP is the one to receive the wireless signals from the indoor and outdoor sensors.
To roll your own you get a TP-LINK MR3020 (currently $28 on Amazon), and license MeteoBridge software (65 Euro for first 2 years, 19 Euros every two years after). Total initial cost can be as low as a little over $100, which is cheaper than WeatherBridge.
WeatherBridge comes pre-loaded with SW, but is just rebranded and otherwise identical. You'll still have to pay every 2 years later on as the license is the same as MeteoBridge. There is also a MeteoBridge PRO, an integrated SW/HW solution that removes the need for the TP-LINK, and has more capabilities for historical data and graphing.
Not only does MB have more abilities to upload to many other weather services, it also has more flexibility in what it uploads, how often, etc. Also can handle weather cameras and uploading of their images and more.