The ISS talks to the Envoy via a proprietary wireless link so you have to have those two items if you aren't running a console. I would use the Envoy to connect to my LAN network where I can use compatible 3rd party software to log the data. So, I don't need the Davis WeatherLink IP software. Let me know if I got this part right. For the data logging software, I hear good things about Virtual Weather Station and it's much cheaper.
Instead of using a console, I would prefer logging software that supports android and IOS apps. The app would pull data from the logging software and display it. Surely this already exist?
I have similar functionality with my security camera software. The software runs on a Dell server where I plan to also install the data logging software. I have ports forwarded in the router to the server so the app can connect from outside the network as well.