Sunrise is a cross-platform calendar app for Mac, iOS, Android, and the web that consistently gets rave reviews. On the iOS side of things, though, the latest update to the app is so brilliant, you might love it even if you hate Sunrise. It's called Sunrise Meet, and it's a keyboard extension that makes scheduling meetings a snap.
Instead of switching between your calendar and iMessage to laboriously type in a bunch of different possibilities, Sunrise Meet replaces the keyboard at bottom of your screen with a calendar. Just tap the empty blocks in your calendar to suggest possible meeting times. When you're done, Sunrise dumps all those possibilities into a web link, which is then copied into your iMessage. When the person on the other end clicks on the link, they get to select what time works for them. The agreed upon appointment is then added to your calendar.
If you have a busy calendar, it's really impossible to describe how slick this execution is:
The sly brilliance here is this keyboard extension is a great way to win users to Sunrise's calendar service, even if you don't want to use it as your main calendar app. For example, I love Fantastical's lightning quick and accurate natural language appointment entry: just type "Call with Suzanne every other Tuesday at 4pm starting two weeks from now" and it'll figure out the rest. Sunrise isn't as good in that regard, in my opinion, so I'd never use it as my default calendar app.
With Meet, though, you don't have to. Because Sunrise interacts with your online calendars like GCal and iCloud without replacing them, once you set it up, the Meet calendar is just a tap away no matter where you are: email, iMessage, typing into a web forum, and so on. That means even if you use another app for your calendar, Meet is still enough to convert you into a Sunrise user. It's win-win.
But my wonderful editor Adrian Covert makes another excellent point. Unlike the Microsoft Surface, iOS doesn't allow you to have true split-screen multitasking. An iOS app always takes up the whole screen, so you can't, say, browse Facebook while also watching a movie. But apps like Sunrise Meet have seemingly figured out something that even Apple hasn't: by using the keyboard extension functionality in iOS, developers can run their apps on the same screen as other apps, even if those other apps don't want someone else crowding their screen. For apps like Sunrise, the iOS keyboard could be a Trojan Horse into true multitasking.