But they could give more people a taste of VR and make better games and applications affordable.
On Wednesday, Google said it will develop a range of VR headsets that promise to be more comfortable and durable than its ultra-cheap Cardboard headset. Google will make one and share design guidelines with other manufacturers.
There will also be a wireless motion controller - functioning like a fishing rod, a steering wheel or a pointer - to permit more-sophisticated VR experiences.
Sophisticated systems such as the Rift and the HTC Vive are expensive, limiting their appeal to gamers and other tech enthusiasts. Alternatively, cheaper VR headsets that tap the power of smartphones are typically tied to one manufacturer's phones, such as Samsung's or LG's.
Daydream headsets will work with a range of phone brands. Gartner analyst Brian Blau says he believes the Daydream-powered devices could prove to be a "thorn in the side" of both Samsung and Oculus, which teamed up to make a similar VR headset , called Gear VR, late last year.
But there are hurdles:
You must buy a new phone
You'll need a higher-end phone running the upcoming "N'' version of Android. Existing phones won't have the right hardware, and cheaper "N'' phones won't either, so you might have to spend a few hundred dollars more for a top-of-the-line model.
Because these phones don't exist yet, it will take time for Daydream to grow, says Jan Dawson, chief analyst at Jackdaw Research.
Furthermore, Daydream won't work with Apple's iPhones, whereas Google Cardboard headsets do.
If anything, Daydream could spark interest in smartphone upgrades. Because the pace of phone innovation has slowed, some people have been holding on to their phones longer.
Cheaper, but not cheapest
Though no price was announced, the Daydream headsets will be more expensive than Cardboard, likely in the ballpark of Samsung's $100 Gear VR. By contrast, Google sells Cardboard for as little as $15, and many brands, including The New York Times, give them away as part of promotions. The price difference gives you better materials - not cardboard - and a strap to keep your hands free.
Still, the new headsets will be much cheaper than high-end VR systems like the Rift and the Vive. Those cost several hundred dollars, not including a powerful personal computer with fast-enough graphics.
It's not full VR
You won't get everything you get with higher-end systems. The Vive, for instance, offers full position tracking. As you walk around a room, images on the headset change to reflect your new perspective.
By contrast, smartphone-based VR is more like a 360-degree movie in 3D. You're meant to watch it sitting down at the same spot. Moving around won't change the perspective.
It's the difference between climbing Mount Everest by gripping virtual ladders, or watching someone with a 360-degree camera do it.
Where Google's system advances over other smartphone headsets is in its motion controller. Cardboard and Gear VR don't offer much control beyond pushing a button on the headset as you move your head. Google's controller will be able to sense motion, so you can swing it like a tennis racket when playing a tennis game in VR.
The compatibility question
The introduction of yet another VR system might create more confusion and persuade some people to wait until it's clear which will survive. After all, no one wants to be stuck with VR's equivalent of Betamax recorders after the world has moved to VHS.
On the other hand, these headsets are cheap enough that consumers aren't taking a huge financial risk, certainly nothing near what it takes to commit to a Rift, Vive or Sony's upcoming PlayStation VR, says Ian Fogg, head of the mobile analyst group at IHS.
And while some people might be buying VR games and apps that won't work with a future, competing system, Fogg says these are cheap, too - priced like a phone app, along the lines of a few dollars.Better apps, but not the best
And the motion controller could lead to better VR experiences, ones where you do more than sit and swivel in a chair to look behind you.
But you'll need something far more sophisticated to unlock the true power of VR.
"You miss out on rich graphics, the fully immersive audio and the fully simulated environment," says Jason Paul, general manager for the VR business for Nvidia, which makes chips powering the graphics behind the Rift and the Vive.
But Paul is supportive of mobile headsets, given that casual users aren't likely to experience a sophisticated VR device.
"Each has their value," he says. "We can use the mobile platform to get the word out."