I've not seen many people blog about this API in iOS 9 for checking the low power state of an iOS device, but Jake Marsh took up the challenge this week. It's not a very complex API (in fact, it's pretty trivial) but it's possible you've overlooked it and it might be that your app could be doing less while it's low power mode. Being respectful of battery life is going to make your users love your app even more.
Obviously its easy to share model and other non-UI code between iOS and tvOS, but what about view and view controller code? All while respecting the UI guidelines and device restrictions of the different devices. Manuel Marcos has a great post here on some exploration of how to make this work, along with a sample project for you to check out.
Logan Wright talking about getting up and running with Vapor, a new server side framework for building web apps in Swift. There's still clearly a long way to go until I'd consider doing anything more than experimenting with these frameworks, but some are on their way to being interesting.