Auto night mode: iBooks in iOS 7 offers a night mode with gray-on-black text that's easier to read in dim-lighting. iOS 8 takes that up a notch with an auto-night mode that can presumably flip over to that night setting when it recognizes that you need it--though whether it does so simply by time of day or by looking at the ambient light around you, we don't yet know.
Though mentioned briefly at the end of the iOS 8 presentation, Siri looks to be getting its own improvements here and there. Its new "Hey, Siri!" command will let you summon your voice-activated assistant without a button press (if your device is plugged in or already on the Siri screen)--and in 22 new languages, too. (If it's just dictation you're performing, you'll be able to do it in 24 new languages.)
In addition, Siri will soon be able to recognize what song is playing on the radio thanks to integration with Shazam, even letting you purchase the song on the iTunes Store if you don't already own it. And, taking a nod from OS X's Enhanced Dictation, Siri will recognize and transcribe words as you speak, rather than waiting for you to complete your command.
Private browsing per tab: In OS X Yosemite, Safari now offers the option to create a new private browser window. Obviously, iOS doesn't have windows, so it offers the next best thing: private browsing on a tab-by-tab basis. That way you don't need to switch your entire browser over to private mode when you need to view a sensitive website, such as your bank's. Instead, you can just devote a single tab to it and be confident that, when that window's closed, your privacy will be maintained.
RSS feeds in Shared Links: As with OS X Yosemite, Apple is once again bringing back support for the RSS syndication service--this time building it into Safari's Shared Links section. When you come across a link to an RSS feed on a website, you'll be able to tap on it and add it to Shared Links, where it will be commingled with any links from social networks that you've set up there.
DuckDuckGo support: Apple's once again expanded its search engine offerings in Safari, adding this simple, streamlined site--particularly well known for its emphasis on privacy--to the likes of Google, Yahoo, and Bing. We presume you'll be able to choose it as a default in the Settings section of Safari.
Battery usage by app: Want to know which of your many apps are really chewing through your battery life? Just as iOS 7 brought us a breakdown of cellular data usage on an app-by-app basis, iOS 8 is doing the same, but for battery life. Hopefully this will make it easy to avoid vampire apps and keep your battery running longer.
In case of emergency card: Included in iOS 8's new Health app is a card containing important personal medical details, such as existing conditions, allergies, and emergency contacts. It's one of those features that you hope you never really need, but would be plenty glad it's there if you do.
Calling, communication, and travel
FaceTime call-waiting: If you're a popular FaceTime conversationalist, you may find yourself receiving an invitation to talk while you're already on a call. iOS 8 will offer call-waiting for those video (or audio) chats, meaning you could put your current conversation on hold while you field a new one.