Welcome to the WeatherCat forum, David!
The other guys have hit the three low-cost options for shopping. Davis doesn't allow advertising of best cost, which is why you have to email them for their best price offers. It is worth the effort, as you will probably save a few hundred dollars on your list of components.
Instead of the expensive Davis tripod and mast, go to your local Radio Shack and get their 5 foot tripod and 5 or 10 foot mast. It will save you some money, and is of good quality. You plan on mounting the ISS on a tripod? Is this for portability, or is it also going on a roof. Note that there is some maintenance needed on the ISS, so good access is nice to have. Optimal location for the ISS is about 5 feet above ground level.
Your mileage may vary on the signal strength for your Envoy location. Modern houses with extensive wiring (and ins some cases metal studs) may interfere with the signal. Only through trial and error will you know for sure.
The Envoy works fine as you plan to use it, but note that you will need to install and run WeatherLink for Mac to set up the Envoy's elevation, barometer, and maybe a couple of other settings. An option is to use the similarly priced Vue Console. But be sure what, if any, other sensors you plan to add in the future, as the Vue Console is not as flexible as the VP2 Console. I ended up buying a second VP2 Console for here on my desk, while the original is in the kitchen, as I have a soil station in the garden.
Another option instead of the Envoy is the Weatherlink IP, which you can attach to your network router and access via wifi for your min or any other Mac on the network. More costly, but might be an option if the Envoy isn't able to maintain a good signal at your desired location. I'm not sure of the WLIP's flexibility with additional sensors.
24 Hour FARS is a nice feature if you are in a location with heat and humidity in the summer and still air. The fan keeps the air circulating past the sensors to give a more accurate reading.
Solar and/or UV sensors are more expensive to add on after the fact, so if you think you will want them some day and can spend the extra up front, it will save you some money.
And you've already found the best Mac weather software available, so no need to offer suggestions there!
As you can see, we enjoy spending other people's money.
We have a very active user community here, and the developer is an active participant. Many members have developed templates for web pages, AppleScripts, iOS apps, and more.
Welcome aboard,
Steve
