It's great fun building the app, and yes, aiming to support Android & Windows in good time. As iPhone's are far and away the most popular, Apple is the platform that gets attention first.
Regards the "existing" mobile app .. yes, by all means - point your mobile browser at m.seabreeze.com.au and you'll get a sweet cut down view of the site (no top or side pesky menus) and minimal bandwidth usage. (Or continue to use the full site).
There's a link at the very bottom of every page (quite hidden) titled "Mobile Weather Site" which you can click on, inside your mobile's browser (to save you typing).
Regards iphone -vs- htc -vs- windows. Yes, they all have inbuilt browsers which are excellent, and get the job done perfectly well. After experiencing the goodness of a dedicated app, Apps are definitely the way to go, plus, the App will feature some new groovy stuff, but more on that when it's more reality than imagination!

Enjoy .. Loz