When using one of Google's new Lollipop-powered Nexus devices, something will become apparent: Google doesn't seem to like power buttons. The Nexus 9 has tap-to-wake, and the Nexus 6 uses ambient mode to wake the screen when you pick it up. Then there's the complete lack of settings in the power menu when you long-press the button. It's almost like Google is demoing ways to deemphasize the power button—and maybe that's exactly what's happening.
What would happen if Google killed the power button completely? The bold idea could work with surprisingly few modifications to the way Android works.
Waking up without a button
Rousing your phone from slumber is a problem that already has multiple existing solutions. Google seems to be experimenting with tap-to-wake and accelerometer detection (ambient display), and these both work pretty well already. LG also uses tap-to-wake as part of its Knock Code screen feature. The touchscreen or accelerometer can be kept awake at the kernel level to detect these interactions.
HTC has come up with a way to keep you away from its inconveniently placed power button on the One M8, too. You can wake the phone and unlock instantly to various screens by swiping in different directions on the screen—HTC calls this Motion Launch. For example, swipe up to unlock, to the right for BlinkFeed, and to the left for the home screen.
Motorola has a particularly excellent solution on its flagship phones. Moto Display includes the ability to wake the screen automatically each time you pick it up, so you can easily unlock it with one swipe. Moto Actions sweetens the deal by using IR sensors to detect movement, so you can just wave at the phone and the screen will wake up.
If you combine a few of these ideas (especially Moto Actions) you could basically avoid ever touching the power button to wake up a phone again. That's the easy part, though. How do you put it to sleep?
Going to sleep, button-free
There aren't as many options for putting a phone to sleep without a button as there are waking it up, but there are a few plausible ways to solve this. LG already has a feature called Knock Code that lets you wake the phone up with a series of taps, but it also includes the ability to turn the screen back off by double tapping in any empty spot on the launcher or on the status bar. It's not the most elegant solution ever devised, but the G2 and G3 are interesting models for a phone without a power button. Both these devices have a rear-facing button that is inaccessible when the phone is laying on a surface, so LG had to come up with something. This isn't bad for a first attempt.
Ideally, a phone would simply know when you were done looking at it. Samsung has tried to use face tracking in recent years to shut the screen off when you're not looking, but it has never worked terribly well. Motorola is doing the same basic thing now on the new Moto X, and it works a little better. In a dark room, though, it's a lost cause. Surprisingly, the key to making this feature work properly could come from one of this year's biggest flops: the Amazon Fire Phone.
For all its flaws, the Fire Phone has killer head-tracking technology. Granted, Amazon used that to power its wonky dynamic perspective screen feature, which it turns out no one wants. However, the infrared LEDs it relies on can help the phone see you even in the dark. If you combine that hardware with the face tracking features in devices like the Moto X, you could have a phone that knows to shut off when you are done using it. Imagine, the phone wakes up when you touch it and goes to sleep when you set it down. Who needs a power button?
Have you tried turning it off and on again?
Turning a phone without a power button on and off are probably the easiest problems to solve. It would be far too annoying to remove the volume toggles, so why not make a combination of volume up and down the same as a power button press? For example, press up-down-up to power on a phone. Or long-press the volume up key. That's an easy way to turn a phone on without a dedicated power button. Phones are fully powered down seldom enough that the power-on function doesn't have to be especially fast.
You have even more options when you want to turn a phone off or restart it. These functions can be handled through software, maybe with a button in the Quick Settings panel. A lot of devices already have the ability to do this entirely through software, so we're good on that front, but what about when things go wrong?
If a phone locks up or you need to access recovery mode, mashing the power button can be both effective and cathartic. In the event of a serious failure, we'd either need to use some gimmick involving the volume toggles to again act as a hardware power button, or there could be a small reset switch akin to a SIM slot (although that seems to defeat the purpose a little). There are ways to get around the power button even in this extreme scenario, so maybe in the not too distant future you'll have an Android phone without a power button to mar the design.
With the solutions already on the market, we're almost there—a phone that is practical and easy to use with no physical power button could conceivably happen today. We don't think Google's actually attempting to push Android in that direction, but the Android ecosystem is trying to make reaching for the power button obsolete.