Calling the Nexpaq "the next best thing" after Project Ara may be unfair, because rather than forcing you to pick up a brand new phone, this versatile case has the advantage of letting you add handy features to a device that you're accustomed to. And of course, from a business standpoint it makes sense to go right after the biggest existing user bases, courtesy of Apple and Samsung. The Nexpaq team wants to keep its products super affordable, after all; even if you miss the $89 early bird offer, the starter package is just $109 and comes with four featured modules. As mentioned, the catch is that at the moment this is only available for the iPhone 6, the Galaxy S5 and the Galaxy S6 Edge.

The base case has a built-in 1,000 mAh battery along with six module slots, each using a customized connector that can be plugged in and out for at least 10,000 times. The startup already has a wide range of modules to offer: a 400 mAh battery, an amplified speaker, a powerful flashlight (with six multi-color LEDs), a microSD card reader, a temperature plus humidity sensor, a pair of customizable hotkeys, a 32GB USB flash drive (with built-in USB plug), an air quality sensor, a breathalyzer, a laser pointer and a 32GB backup memory module. Needless to say, these modules are OS-agnostic, so you can swap them between the Samsung cases and the iPhone 6 case.

Most of the bundles in the Kickstarter campaign come with the loudspeaker, battery, hotkeys and microSD reader modules, with the rest being optional, ranging from $14 to $29 per piece. And there's also a $3 dummy module, should you struggle to decide how to occupy the last remaining slot.

The possibilities are limitless. Co-founder and Chief Strategy Officer Hubertus Wasmer sees great potential in developing a range of medical modules, which can greatly lower hardware costs while increasing portability, meaning doctors can easily carry a tiny lab to remote areas in third-world countries. The same goes for environmental sensors.

A prototype Nexpaq modular case shown alongside its companion app with non-final UI.

Unlike Project Ara, there are no fancy electropermanent magnets on the Nexpaq. According to CEO Alex Murawski, this technology is far from ready, and not to mention that it'd add up the cost. What you get instead is the good old slide-in mechanism that's surprisingly secure on the prototypes we played with.

The status of each module is displayed in the companion app. Interestingly, this part is actually done through Bluetooth Low Energy, but the usual data link is through the micro-USB port or the Lightning port. In a live demo given by Murawski and Wasmer, the app responded almost instantaneously as they shuffled the modules around. It's as if you're slapping on various IoT sensors onto the back of your phone. Developers can also take advantage of the app's online store to offer new modules to consumers.

Nexpaq co-founder and CEO Alex Murawski.

Nexpaq is no doubt a very ambitious project, but it's also a solid one with good intentions. Prior to this startup, Murawski had already worked on eight other crowdfunding projects -- including the Nomiku immersion circulators -- for his clients at his other company, NOA Labs , so R&D and manufacturing aren't a problem. Wasmer also stresses that Nexpaq is an open platform, and it's all about vastly lowering the cost of gadgets for both makers -- hence the development kits -- and consumers. For us, we just need to convince this startup to make cases for more phones and maybe even tablets.