I’m not sure what build this was first incorporated into (for all I know it’s been around for a long time) but if you use the default WM dialer and have the lock screen on then these are the screens you are greeted to when using the phone. As you can see, there’s a slide to answer feature when you get an incoming call. And during a call you get a large finger friendly interface that’s actually pleasant to use. I know that there are some functions missing from these screens, like the ability to respond with a text to an incoming call or turn on video sharing during a call, but I sort of like these screens overall for their simplicity and ease of use.
If the lock screen is off or if you accept the call then you’re back to the traditional WM dialer, but it’s a start. If you have another dialer enabled (like HTC’s dialer) then the slide to answer will not work but the lock screen can be enabled if you lock your phone when the screen dims for example. If you want to use these as your primary dialer you should make sure your dialer still functions once the standard dialer is enabled. I found that the stock dialer didn’t pull contacts correctly so dialing was tricky.