Just wanted to say thanks for sharing this. I've been wanting to do a menubar app that uses Forecast.io's API but I have little to no experience with Obj-C so just having something to go off of will help me in learning.
I saw this before deciding to build my own... it's just a webview and is a lot slower than mine. My app is completely native with no webviews whatsoever. So faster and less memory intensive :)
http://www.guidefreitas.com/hacker-news-menu-tab-app
I've been using this for a bit and it's pretty neat. Also not required to use the Mac App Store to install it.