Update: During its WWDC 2015 keynote, Apple announced that CarPlay will soon go wireless – no need to connect to your car's USB port. However, the company didn't specify whether this connection would occur over Bluetooth or another wireless connection protocol.
The firm also announced that CarPlay will soon support a wider range of screen sizes and resolutions, not to mention apps developed by the auto makers themselves.
Original story follows...
The first Apple CarPlay cars are beginning to roll off the assembly line following the much-mooted "iOS in the Car" project announcement in March 2014.
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With our digital tech barely having made a scratch on the largely analogue in-car experience, the automobile is considered by many to be the next great tech battleground along with the Apple Watch.
Because the lifespan of a car is so long compared to the lifecycle of digital technologies like phones and the software they run, the challenge is to create a smart in-car infotainment system that can stay up to date even as your car ages.
Most of the big names in the auto industry have their own systems, but in the last couple of years they've all been converging on one simple idea – that smart in-car tech needs to be driven by our external devices because they get updated regularly, with the car being just the passive conduit.
We've already seen several Android Auto in action, offering integration with Android smartphones. And that now brings us to Apple CarPlay, a new way of building a car that starts smart and stays that way.
What is CarPlay?
CarPlay is not an in-car system that runs iOS or iOS apps. It's a system that integrates your iPhone apps with your car's digital systems, allowing you to control them and your device, more easily.
The idea is that you plug your iPhone into your car via a lightning cable, and it instantly handshakes with your vehicle. You can then use the functionality of your iPhone without having to fumble around with it and take your eyes off the road. It's safer, easier and more convenient - or that's the idea, anyway.
What can CarPlay do?
The idea of CarPlay is that it allows you to use all your iPhone's functionality without actually touching it. So that includes playing your music, navigating to the shops, taking phone calls, reading and text messages.
In theory, there are no limits to the interplay. Perhaps you'll even be able to turn your wipers on and off simply by talking to Siri or unlock your vehicle using your iPhone - but that's a way off even if it's possible.
From the start, you'll be able to use your iPhone's phone and messaging functionality, play your iTunes music, navigate using Apple Maps and watch videos.
However, Apple's plan is to allow third parties to build CarPlay compatibility into their apps, making them usable through the system.
Confirmed apps with CarPlay features incoming are: Spotify, Podcasts, Beats Radio, iHeartRadio and Stitcher. Expect a smorgasbord of other options to be revealed in time - we foresee a future where all relevant iOS apps are built with CarPlay in mind.
How do you control Apple CarPlay?
There are three ways to control CarPlay, and none of them include touching, looking or even thinking about your iPhone.
1. Control CarPlay using Siri
Using Siri, you'll be able to talk to your vehicle and tell it what to do. That includes playing music from your favourite band or even requesting a specific playlist. You'll also be able to have your messages read out to you before you dictate your reply.
2. Use a touchscreen display
Some CarPlay cars will come with touchscreen displays cooked into the dashboard. Using this display, you'll be able to open and close apps using a very simple homescreen. This will certainly be the most straightforward method of using CarPlay - expect touchscreen options being added to new car models.
3. Use your knobs
Of course, your car will still have physical buttons, knobs and controls and you'll still be able to use these alongside the touchscreen and Siri options. Volume controls, track skip and the like are all seemlessly integrated and will work as expected.
Can CarPlay drive me home?
CarPlay is not a driverless technology. So the command "Siri, drive me home" will no-doubt simply trigger a typical pre-planned sarcastic Siri response. "You.. are.. having.. a.. laugh.. aren't... you...David?"
However, what CarPlay can do, is use your iPhone's Apple Maps app to guide you while you drive. If you have an in-dash display, the Maps app will launch a sat nav style window that will give you turn-by-turn guidance without you having to put your iPhone in your field of view. If you don't have a display, you'll still get the turn-by-turn audio cues.
Is my iPhone compatible with CarPlay?
Apple CarPlay requires a certain amount of oomph and a lightning connector, so older iPhones with a 30-pin dock connection are simply not capable of running it.
Are there any CarPlay cars yet?
The singularly and therefore appropriately named CarPlay is riding solo right now. Only one automaker supports Apple's in-dash system.
The expensive Ferrari FF is the first and only commercially available vehicle in the world with Apple CarPlay.
Yes, Mercedes and Volvo were revved up to deliver the same iPhone-compatible experience in 2014, but were delayed into next year with the rest of the pack.
On the upper-end, the Volvo XC90 SUV and Mercedes-Benz C-Class will join Honda, Hyundai and Jaguar models, which have been set up for a 2015 release date since the beginning.
We've seen both the 2015 Hyundai Sonata and 2015 Chevrolet Volt with both Apple CarPlay and Android Auto side-by-side, and fully expect more commitments from BMW, Cadillac, Chevrolet, Ford, KIA, Land Rover, Mitsubishi, Nissan, Opel, Peugeot-Citroen, Subaru, Suzuki and Toyota.
Volvo has posted a cool CarPlay video:
Can you get CarPlay for your existing car?
Just bought a car? Fret not. Apple CarPlay aftermarket solutions are coming from companies like Alpine and Pioneer to make existing cars compatible with iPhone's in-dash experience.
CarPlay support in these receivers will arrive in the form of a firmware update to Pioneer's existing line of 2014 NEX units, which range in price from $700 (about £449, AU$861) to $1,400 (about £900, AU$1,730).
Additionally, Mercedes is one automaker that said it'll soup up its existing cars. It's already committed to installing CarPlay in its C-Class vehicles and word is that it's building a unit that will allow current Mercedes drivers to make use of the CarPlay technology.
Are there any rivals to CarPlay?
Predictably, Google is already heavily involved in this space. In fact, with its huge investment in Google Maps and driverless car technology, some would say that Google is already well ahead of Apple when it comes to in-car tech.
After a side-by-side test drive comparison, we found that Android Auto has two advantages: it features Google Maps and a slicker Google Now-powered interface.
But Android Auto isn't street legal in existing cars at the moment, with the 2015 Hyundai Sonata vying to be the first to use Google's system. It's also only available to Android users.
What does Apple say about CarPlay?
"CarPlay has been designed from the ground up to provide drivers with an incredible experience using their iPhone in the car," said Greg Joswiak, Apple's vice president of iPhone and iOS Product Marketing.
"iPhone users always want their content at their fingertips and CarPlay lets drivers use their iPhone in the car with minimized distraction. We have an amazing lineup of auto partners rolling out CarPlay, and we're thrilled it will make its debut this week in Geneva."
As Apple CarPlay arrives in 2015 cars that aren't as expensive as the Ferrari FF, we'll continue to test drive iPhone's official in-dash experience and update this page and see how it compares to Android Auto.
Joe Osborne also contributed to this report