Well, you've got one out of two already. :) Apple laptops can be powered by Apple external monitors.
It'd be nice to have a more "universal" standard -- where I'm sitting at work right now I see one coworker with a ThinkPad plugged into an Apple monitor, and another with a MacBook Air plugged into a Samsung monitor, and that means both of them need one more outlet than I do. But that's a meeting of the brands I wouldn't hold my breath for.
> Well, you've got one out of two already. :) Apple laptops can be powered by Apple external monitors.
Well. Kinda. You still have to plug in two cables. This would allow to go down to one single cable powering the laptop and sending signals to the screen.
Though, honestly, I don't trust USB to be a good protocol for transmitting a high bandwidth and very lie latency signal with it's inherently polling architecture.
Isn't that the whole point of USB's isochronous transfer mode, where a peripheral schedules part of the total USB bandwidth budget for a regular transfer of data? USB 3.1's got similar bandwidth to Thunderbolt and HDMI 1.3, so that could work for many video applications, although not for uncompressed 4K/60Hz, although VESA Display Stream Compression could allow it to work.
It'd be cool with a laptop, but it'll require an extra 20 watts (typical for a ~22" screen) to be sized into the laptop's power brick. Since laptops have pretty predictable power characteristics, the manufacturers don't necessarily give you that much extra.
Would we upsize everybody's power cord on the off chance that 1% of people would use it? Or does "bigger power brick" become another configurable option, and users have to decide in advance if they'll want display powering capabilities? Neither one's a good option, in my opinion.
More likely we'd end up with a separate class of monitor, something limited in size and with a lower maximum power draw. At which point I'd rather just deal with the power cord and get a real screen for my desk. But frequent travelers who want an accessory screen would love it.
I think what will be more likely is the other direction. The monitor powers the laptop. Most laptops are well under a hundred watts and could easily be charged and powered that way.
Which is a great new other feature of USB Power Delivery: peripherals can provide bus power. This way you might have an external USB monitor (USB A/V you were announced 2011: where the _hell_ are you?!) that also provides power.
For a while it seemed like DisplayPort or DockPort might be the one cable to rule them all... USB PD seriously changes the footing of the game. Alas, USB A/V (encoded video to an output device) being completely absent is seriously damning USB's chance to be that one cable.
Experience dictates that about 95% of manufacturers will be too cheap to implement that bus power on their devices, because it'd cost them 50 cents more. So it won't matter much.
> Even cooler, would be driving an external monitor from a smartphone.
That will be expensive though. You'll have to pay the medical bills for getting your back fixed after having to carry the suitcase with the batteries :).
Current cell-phones have batteries around 2 Amp-hours. At 5 volts, that's 10 Watt-hours. The least-power hungry display according to [1] is a 15 inch LED; it clocks in at 15 Watts. This means you'd be able to use your external 15 inch display for 40 minutes before completely draining your battery. That is not counting anything the phone is actually doing, just powering the display.
> Even cooler, would be driving an external monitor from a smartphone.
I worry somewhat about the smartphone's battery in this context. I wonder if any have good 'passthrough' for when the battery is full and a wall socket is connected - even then I doubt it. :/
Even cooler, would be driving an external monitor from a smartphone.