The concept of a modular smartphone that lets you quickly swap in components like a bigger battery or better camera has been around for a few years now, but the best-known example — Google's Project Ara — is still firmly in the prototype stage. Now, however, a new Kickstarter campaign is offering consumers a modular smartphone product they can actually buy and (hopefully) start using in a few months. This isn't a modular smartphone, however, but a modular smartphone case. Meet the Nexpaq.

From the rear, the Nexpaq looks similar to the Project Ara prototype . There's a central spine down the middle and open slots on both sides for the add-on modules to fit into. The case itself is available for three smartphones (the iPhone 6, Galaxy S6 Edge, and Galaxy S5) while the modules — 12 of which are available at launch — are all iOS- and Android-compatible. They're also hot-swappable, meaning users don't have to power their phones on and off to change them, and the case itself comes with a built-in 1,000mAh battery as standard. This isn't as good as a dedicated battery case , but Nexpaq says it adds 30 to 60 percent extra charge, with a battery module adding another 30 percent.

MODULES INCLUDE THERMOMETERS, FLASH DRIVES, SPEAKERS, AND LASERS

Nexpaq is also hoping to build a community of third-party developers to make modules for the case, and is releasing a toolkit and API to encourage this. Thankfully, the Nexpaq certainly isn't lacking in functionality to begin with. The launch lineup includes a battery module, a speaker, an LED flashlight, an SD card reader, a thermometer and humidity sensor combo, and a module that functions as a pair of programmable buttons. There's also a USB flash drive, an air quality sensor, a breathalyzer, a laser pointer, a 64GB storage drive that plugs directly into your phone, and a dummy module for slots that aren't in use. All of these are controlled via Nexpaq's app, which also works remotely over a Bluetooth connection when the case isn't on a phone.

While all this seems fantastic on paper (even the case itself looks pretty slim), with so much extra functionality, there's a lot that could go wrong. As well as build quality, would-be customers might worry about the usability of Nexpaq's app and the accuracy of the instruments themselves. Has Nexpaq really managed to create a reliable breathalyzer the size of your thumb? Does the tiny speaker module actually sound good, or will it just double down on your phone's tinny audio? Nexpaq has told The Verge that the modules are rigorously tested to meet "international quality and warranty standards," but questions like these are often best answered by reviewers.



The Nexpaq looks great on paper, but questions about quality remain

Intrepid customers can order a Nexpaq at an early-bird price of $89 for a case and four basic modules (battery, speaker, buttons, and an SD card reader) or pay extra for more cases and modules. Backers can top up their orders with individual modules, priced from $14 for the laser pointer to $29 for the 32GB USB flash drive. Shipping dates for the Nexpaq are variable however, with the $99 "Beta Bundle for iPhone 6" set to ship in November this year, while Galaxy cases won't be sent off until January 2016. Developers who want to get their hands on a Nexpaq extra early can shell out a whopping $2,999 for a case and all 12 modules, scheduled to ship in June 2015.