Powerwall Companion is a Windows UWP app for monitoring your Tesla Powerwall 2 battery. It has similar functionality to the official Tesla app for Android/iOS, but it's designed to be more of an "always on" dashboard. The app was originally developed to run on Windows Phone, but now that OS is no longer supported, the app only runs on Windows 10+ PCs. If you want to run this on a phone, check out the Android version: (Store | Source)

The app is available to download from the Windows Store here. The store is the easiest way to get the app, but I'm sharing the source in case anyone wants to improve it or is curious about the underlying APIs.