The CarPlay interface is undoubtedly better for using while driving than the regular 'ole screen. But unless you've got a shiny new car (or one of the expensive aftermarket dashes), chances are you don't have anything to pair your iPhone with. But this tweak gives you an idea of what CarPlay would look like running on just your handset.
There's some bad news, though: you'll have to jailbreak your phone if you want to download the tweak. The software, called CarPlay iOS, is pretty simple to use: after downloading, you get a CarPlay app on your home screen. Launch it, and you're thrown into the CarPlay interface, which runs in landscape.
At the moment, functionality is limited to just the music app, but there's hope for the full feature set. The devs behind the CarPlay iOS software have said that the current build is just a preview, and they're working on adding full functionality. Another developer, Adam Bell, has also been working on a similar solution, and posted code to GitHub last month outlining his plan. IDownload Blog has a good video explaining the current version in full:
Hopefully, this will come to fruition, and someday even become an option for those of us not yet surrendering to jailbreaks. CarPlay's a much better interface for driving than regular iOS, and truth be told, I can imagine an iPhone 6 Plus mounted in landscape would make for a pretty great dash controller. Just, y'know, no texting and driving, mmkay? [iDownload Blog]