Review: The one killer feature that should've been in the latest iPhones, but probably never will

I've had a few days to play around with the iPhone 6S now, and by far the most engaging feature I've used has been Apple's Peek and Pop. Beyond the simple right-click actions you get access to from the home screen, Peek and Pop goes further, with Apple's 3-D Touch technology, by letting you preview emails or text messages right from the inbox. It's a great way to save a step if you, like me, get a gazillion emails every day clamoring for your attention.

Developers have spent millions of lines of code trying to reinvent email. The hot design convention du jour is the swipe - swipe left to mark as read, swipe right to archive. This is a highly efficient way to handle spam or messages you're sure you want to ignore entirely. But what if you aren't sure? What if you need to know a little more before you make a decision?

This is where Peek really shines. It gives you more information than you'd get from a short subject line, but it doesn't require committing to the message. (Certain mail apps will wait to download the full email until you click to open the message. In my experience, that's led to frustrating waits while the app fetches the message from the server, when all I wanted to know was whether I could move on.)

Peek allows you to get the gist of an email quickly. The more I used it, the more I wished it was everywhere. Which brings us to where it's not - and noticeably so.

The one place I'd love to see Peek used more is on the lock screen. Lock screens act as a kind of preliminary inbox, showing you a list of incoming messages and alerts. Over time, Apple has given iPhone users the ability to act on these notifications - you can now reply to text messages, for instance, without ever unlocking your phone.

So to be able to check the full contents of a message without going to your mailbox would seem like a logical next step. It makes no sense to have to unlock your phone and head to your inbox before you can take advantage of Peek and Pop. That's a little backward.

Unfortunately, there are two key reasons you aren't likely to see Peek and Pop coming to the lock screen anytime soon. The first is security. If somebody were sending you sensitive information in the body of an email, you wouldn't want Peek to reveal so much of the message without some kind of authentication.

That's the second stumbling block. Maybe someday the iPhone's whole screen will become a fingerprint sensor and it would only enable lock screen peeking if it recognized the owner's prints.

That day still seems a long way off. But we can hope.