How can I know when new iOS updates are released? As a technician, I'd like to learn when an iOS update appears so I can prepare iTunes with all the recent restore images.  Any way to know that? or receive notifications when an new iOS update is released? (better if Apple official).
ipsw.me provides an RSS feed of iOS releases at ipsw.me/timeline.rss. You can subscribe to this RSS feed (or a filtered version) using IFTTT. Templates are provided at ipsw.me/notifications. This is accurate to a couple of minutes.

You can also subscribe to the TSS status of iOS releases using the API available at api.ineal.me. This can be near instantaneous, providing a real-time view of TSS signing (and subsequently the releases).