Most of my friends who own iPads also own iPhones. Apple bet that users would find enough differences between those devices that consumers would want both - and Apple was right.
I think it's rare that a person owns a tablet and not a smartphone. (Hi, Mom.)
Asus is a brand better known for laptops, but its recent introduction of the Padfone X is a reminder that it also makes smartphones and tablets.
The Padfone X is a 5-inch Android smartphone paired with a 9-inch tablet.
The phone slides into the back of the tablet screen.
The tablet itself has no brain. The phone provides the computing power, and the tablet provides the bigger touch screen and a huge battery.
Separately, the phone and the screen are fairly unremarkable, but together, the two gadgets become an interesting concept.
Using the iPhone/iPad duo as an example, the iPhone has all the functionality of an iPad but with a smaller screen (and a cellphone).
Sometimes you need the convenience of just carrying around a phone; other times you want the luxury of using a larger screen.
Until now, you needed to buy two fairly expensive gadgets that overlap a lot of features to get the best of both worlds.
Now Asus is putting it all in one box, and AT&T is the exclusive seller.
So when I say Padfone X, I'm really talking about both the phone and the tablet - they aren't available separately.
The cost is $200 with a two-year contract or $22 to $29 per month with AT&T's Next plans.
THE PHONE: The phone has a 5-inch screen with a resolution of 1920 by 1080 pixels.
It runs a 2.3GHz Qualcomm Snapdragon 800 quad-core processor with 2 gigabytes of RAM and 16 GB of built-in storage and a microSD card slot that lets you add 64 GB.
It's 5.6 inches by 2.85 inches by 0.39 inches and weighs 5.29 ounces.
The phone's battery has 2,300 milliamp-hours of power that gives up to 20 hours of phone use or 19 days of standby time.
The phone has 4G LTE, Bluetooth 4.0 and 802.11 ac Wi-Fi. It runs Android 4.4 (KitKat).
The main camera has a 13-megapixel sensor that shoots 1080p video and a 2-megapixel front-facing camera.
THE TABLET: The pad has a 9-inch screen with a resolution of 1920 by 1200 pixels.
The battery in the pad has 4,990 milliamp-hours of power that stretches the phone's battery life to 54 hours and standby time to 52 days.
The pad has an inch-wide bezel around the screen, which is good for people like my dad who have a tendency to accidentally touch the screen with their big fingers.
The phone slips into a slot on the back of the pad, which results in a hump in the back, but it's not in the way at all when you use the pad in landscape mode.
The phone-to-pad implementation is really well done.
When you want to use the pad, slip the phone into the slot behind the pad's screen, and whatever is on the phone's screen appears on the pad.
CONCLUSIONS: I like the Padfone X.
Just the idea that your phone could slip into a tablet screen is very appealing. All your data is in one place, and you only need to subscribe to one data plan.
If you're in the market for an Android phone and a tablet, I can't think of a reason not to consider the Padfone X. If you're going to spend $199 for a new phone, why not get one that includes a tablet?
I'm an iPhone user, and if Apple had a larger screen that I could dock my iPhone into, I'd buy it in a heartbeat.
Explore further: Indiegogo project 'Switchmate' lets you run light switch from your phone without rewiring