Here is a list of options, in order of increasing features and cost:

For a simple weather station (on the roof) and a console displaying the weather data in one room, all you need is:
Davis® Vantage Vue Wireless Weather Stations (DWVUE)

If you want to display the data on the internet, so everyone can see it, and do not need the console in the room, your can get:
Davis WeatherLink Live (DWL-LIVE)
and Davis Vantage Vue Wireless Integrated Sensor Suite (DWVUE-ISS)

If you want both the data on the internet and a console displaying data in your room, you can instead purchase:
Davis WeatherLink Live (DWL-LIVE)
and Davis® Vantage Vue Wireless Weather Stations (DWVUE)

We also have the more expandable Davis Vantage Pro2 Wireless Weather Station (DWVP) and Davis Vantage Pro2 Plus Wireless Weather Station (DWPLUS) weather station.