Modular phones first started hitting the headlines back in 2013 when Google's then-handset arm Motorola announced the Project Ara platform. After numerous delays and false starts, there are still no Project Ara devices on the market, while LG's own modular effort, the G5, hasn't set sales alight, and startup Vsenn has shelved plans for its own modular device. Is the modular device doomed?
The idea of modular smartphones is simple one: rather than one black box of a handset, modular devices allow users to swap out key components when they're broken or to upgrade them when better components come along.
It also opens the door to greater personalisation or customisation of handsets: if you're the type of person that wants a great camera but you're less bothered about having NFC onboard, then you can make a phone that fits the bill exactly.
Despite selling Motorola to Lenovo, Google decided to hold onto its Advanced Technology and Project group (ATAP), the unit that has been working on Project Ara. Its vision for the project was grand: to build an Android-style ecosystem for hardware, with component manufacturers making modules such as cameras or memory that could be swapped in and out.
The version of Project Ara now slated for release isn't a fully modular device: it's not possible to swap out some core components, such as the screen, but other elements such as camera and speaker can be popped out and replaced.
LG's G5 is also similarly a far cry from the dream of true modularity: core components can't be replaced without sending back to the manufacturer, and there are only two modules available at present (a camera and a high-end audio component). Still, reviews have been largely positive, even if it's not shifting as many units as LG might have hoped.
According to Roberta Cozza, research director at Google, the recent groundswell of interest comes at a time when the smartphone market is slowing down and handset makers are seeking new ways to stand out. "From a vendor perspective, it's creating differentiation in a market where everything looks the same," she said.
For the larger smartphone vendors, modular design is also something of a paradox: they're businesses that exist to sell more and more handsets, but modular handsets offer consumers a way to delay the replacement cycle by swapping out an outdated or broken part.
To really make modular phones contribute to their bottom line, handset makers need to persuade as many consumers as possible to buy lots as many accessories as possible - perhaps to the extent of buying more parts or at greater cost than they would just replacing their phone.
Consequently, the type of modularity in vogue at Google and LG is about having just enough modularity to encourage consumers to buy lots more kit.
Gartner's analyst Cozza said she is unsure about whether modular devices will prove a hit in the broader consumer market. "I'm a bit skeptical about global consumer appeal... I'm asking myself whether consumers really want this, because smartphones are already getting very complex and this would just add friction and complexity into the experience of the phone."
There are those pursuing true modularity, however: two European startups are focusing on building truly modular phones, Netherlands-based Fairphone and Finnish Circular Devices, the company behind the Puzzlephone.
Both are approaching modularity as a way to get consumers to buy less, not more hardware.
Juan Díaz Díaz, one of Circular Devices' cofounders, said that the decision to create a modular handset was borne from the experience of the company's CEO and fellow cofounder Alejandro Santacreu had with a broken iPhone start button.
"There was no option to just fix this simple and cheap part, you have to buy a full phone. That definitely makes no sense, it's like having to change the full car because your windshield is broken or the tyres are worn... Our main goal is to make the device as easy to upgrade and fix in hardware as it is in software, and it's making everything sustainable by design."
For Circular Devices and Fairphone, modularity is a way for handset makers to extend the life of their devices and keep more out of landfill, and both are putting thought into what happens to components when the hardware eventually does reach the end of its life. For the startups, the chief driver for modularity is sustainability, not customizability.
Modularity could also potentially change the shape of the hardware ecosystem: rather than 100 percent of a handset being made by a single device manufacturer and all replacement parts coming from them, modular devices could mean consumers can pick and choose parts from a range of suppliers in the same way as they pick and choose the software they want on their phone.
For Google, which doesn't make hardware itself and is used to acting as a gatekeeper with the Android App Store, that may not be a problem. For others, used to keeping hold of the totality of their hardware value chain, it may not: in other words, don't expect a modular Apple phone any time soon.
Similarly, modularity represents a challenge for the mobile operators too: traditionally, new handsets are used as incentives to get customers to sign up for new contracts. They have to choose whether to embrace modularity as a way of differentiating themselves but perhaps face losing their leverage in encouraging new sign-ups, or stick with the business model they have.
The startups are selling direct to consumers - Fairphone through its website, Circular Devices with Indiegogo - and so avoid such problems (though both report positive conversations with operators).
While the startups may have several advantages over their larger rivals, there's one area where they fall down: they don't have the same scale. Unlike the Samsungs or LGs of the world, small startups can't reach the same amount of consumers. For now, modular devices are a niche product.
So what's the niche?
"The people that are talking a lot about modular devices are people from IT and technology, mostly because the devices that have been shown are for that market... Most people who are interested in the Puzzlephone are part of the technical universe, but not exclusively," Circular Devices' Díaz Díaz said. Those that are interested in the Puzzlephone are usually either techno-savvy or interested in sustainability.
Fairphone was the first company to bring a truly modular smartphone to market, with the Fairphone 2. Has there been any difference between the buyers of the company's first non-modular device and its modular follow up?
The Fairphone 1 was bought by "ethical pioneers" that wanted to support a young startup trying to make more principled smartphones. "It was a very specific profile of people that wanted to support a company they believed in. Now [with Fairphone 2], it's a wider profile of people... One of the profiles is what we call a DIY techie or the optimistic techie: people that are deeply interested in technology but are also often from an ethical perspective, people that interested in making, but also privacy issues -- the social side of technology."
Modular tech may not be a mass market play just yet, but if you're in the middle of the technology and ethics Venn diagram, a modular device might well be for you.