The promise is simple: a mobile video-editing device that would handle video from multiple sources (DSLR/GoPro/drones etc) and offload all the hard work -- like handling 4K video editing -- from your phone, but keep the simplicity of an app. It was popular enough to earn Gnarbox over $500,000 (from nearly 3,000 backers) on Kickstarter. That was two years ago though, and mobile video-editing has come a long way since. Perhaps the real question is whether that promise is still relevant in 2017?

In the past, video editing was something you consciously "did." You opened a dedicated application, probably on your desktop, and got to work. Once you were done, you exported your project, closed the app and sent your video wherever it was going (Vimeo, YouTube, to a client, physical media, etc.). Now, there's a generation for whom video editing is more about deciding which filter to use and how many emojis to add to an Instagram story. The app this latter group is using is probably the same social network they are posting it to.

Gnarbox (yes, that name probably seemed a good idea at the time) helps both these groups achieve their goal. Inside the small, rugged black box is a mini PC with its own (1.9GHz, quad-core) processors, a dedicated GPU, 128GB storage, WiFi, two SD card slots (full-size and micro) and three USB ports. There's no display -- just two feedback LEDs -- but that's where your phone comes in.

In the app, you'll see every video on the Gnarbox browsable by device (internal storage, memory card, USB drive and so on). All the video previews and edits you do on the phone are really happening on the Gnarbox -- but it feels as if all the files are right there on your handset. Making edits is simple: Just swipe down when you want to set a start point, repeat for the end point and then swipe up to send that "clip" to your reel. Repeat, add color adjustment and other effects, re-order to your liking, add music and export. You can now switch your phone off -- the exporting and encoding also happens on the Gnarbox.

Feess hopes the ability to handle 4K video and RAW images will entice pro users and that the app-based interface and ease of use will appeal to serious mobile/social video producers. At $299, the proposition definitely needs to have some sort of return, whether that's a stunning snowboarding edit uploaded to a client right on the mountain, or a "how did they do that?" cut live from back stage (in the influencer VIP, not real VIP area) at Coachella.

I'm neither on a mountain nor at a huge music festival. By now we're crossing the Golden Gate bridge, and I'm recording the traverse with my GoPro hanging out the car window. We briefly stop at a viewing point crowded with tourists before heading to the only beach nearby that AirMap says we can launch the drone on. Essentially, we're condensing what those Golden Gate happy-snappers might do over a few days into an afternoon.

The rugged coastline of the northern peninsula makes for some dramatic shots and a good contrast to the brick-and-mortar maze of the San Francisco skyline. With all our shots in the bag, Feess wants me to make an edit, without him guiding me. He goes to put some kit back in the car, while I sit on a bench and tinker with the app.

Gnarbox has about seven staff right now, but to look at the app you'd think the team was bigger. It's not quite as polished as iMovie on iOS (which edits 4K, but not easily from multiple sources), nor does it quite have the flow of something like GoPro's Quik. But the guts are there, and Gnarbox is improving the app almost weekly.

Sometimes I go to drag a clip with my finger and it sticks where it is, or I tap "back" and end up somewhere I wasn't expecting. But accomplishing my edit isn't hard, and the video I end up with isn't bad for 10 minutes and no real agenda in mind (you can see it below).

One thing I do notice is that my (already-not-great) phone's battery is slipping away faster than normal. A common problem with WiFi-based accessories. The Gnarbox also gets a little warm to touch. Feess assures me this is how you know it's working, and that the heatsink is right under the housing; it's never too hot. There's also a slight hiccup at the end while we try to export the video to my phone from the box. This takes a few attempts, but we eventually get it to work. I'm on Android, and perhaps my phone is too full. After I delete some files, the transfer goes ahead.

It's one thing that a product works, but it's another that it solves a real problem that people have. I can see how this would be useful for certain pro video producers. Those who find themselves out in the field and don't want to bust out a laptop. I can also see that less-demanding users might appreciate the ability to work fast with their files; it does double-duty as a hard backup for one. Skaters who shoot in 4K, but want an edit for sharing right away, for example, have everything they need here.

Then there's me. I have drones and a few GoPros. I take them out often, and then, well, usually nothing happens after that. The files sit on the memory card until once every few months I have a spurt of creative motivation and at least get as far as transferring them to my PC. I can easily see how a Gnarbox would go some way to dissolving that invisible wall between my camera and my hard drive. A problem GoPro, in particular, has been trying to solve for a long time -- culminating in QuikStories and its auto-editing feature. GoPro's going after the most casual user though; Gnarbox is hoping to lure in heavier users.

In the few weeks since Gnarbox has been on the shelves, the user experience has improved dramatically. The number of firmware updates since that launch suggests that Gnarbox is following the Valley habit of shipping something that works now, and build on it from there. It's a risky strategy, but with smaller companies like Feess', it's easier to be nimble.

The very first time I used Gnarbox (immediately after launch a month or so ago) I hit one roadblock and quietly put it back in a drawer. After today, I can see this being something I reach for every time I head out with a camera. Even more so once key features, like using videos recorded with your phone, are added (you can do it right now, but it's a workaround).

For me, though, the best feature of products like this is the inspiration it stirs. Between my GoPro, phone and drone I have enough lightweight gear to record vacations and day trips in ways not imaginable just a few years ago, but I rarely get that far. While adding another $299 piece of kit to that might mean more outlay, and one more thing to charge, if it results in me actually doing something with those videos -- and it really feels like it might -- then that spend suddenly seems like a pretty decent investment.