I own one Nest Protect and plan to add more in the coming months. Main reason: I like Nest and it looks cool . Second reason: I have high ceilings and my wife already experienced the smoke alarm going off and she couldn't get to it to unplug it.
Installation is a breeze (like all Nest products), design great and the app works great. You can name them in different places of the house, so that way you know which on went off. You can silence them through the app and get notifications. Before it actually starts that annoying alarm noise, it gives you a heads-up by a nice lady voice. My HD has the battery version at $79 for a while now.
The Kidde are half the price at $50, and they work with Wink. Don't know about ST. You can't name them according to the place and I don't know if you can silence them through an app. Maybe, if not it wouldn't make a lot of sense for them to have Wifi.