Don't get this confused with the science fiction show by the same name, as Amazon's version helps you do one thing and one thing only: buy more Amazon stuff.
To use Firefly, you open the app and it fires up the camera. Point your camera at anything, like a set of headphones or even a can of sardines, and it will attempt to link it to a product page on Amazon.
However, in testing this didn't really seem to work most of the time, if at all. This notion was OK in the US, it seems, but the UK version just wanted to look at barcodes.
Firefly doesn't just work on physical, tangible items that you can identify with the camera (in theory). When the app is fired up, it can also recognize music, movies and TV shows. As long as the phone can hear sound from your radio or TV, and it can pair it with something in Amazon's store, it will be recognized.
For example, if you're watching an episode of Friday Night Lights and you point the phone toward the TV and allow Firefly to see and hear the TV, it will tell you what you're watching along with a link to buy or watch episodes of Friday Night Lights on Amazon Prime.
The same goes for music. If you're itching to find the name of a song you're listening to, simply open up the Firefly app and place your phone near the sound source. If it's in Amazon's massive library, the song will pop up with an accompanying link to download or listen to the song.
There are other big things that the service can supposedly do - for instance, recognise URLs. Due to being locked to a network, I had the Fire phone along as my secondary device while reviewing, ready to snap a poster of something I wanted to see.
This never happened. I had the phone at the ready for a couple of weeks, but never wanted to use Firefly for posters.
Except one time on the London Underground when going past one on an escalator... which didn't give me enough time to fire up the button. Even if it had, I wouldn't have had the connection needed to search for it.
Firefly is useful, in a sense, because you can identify a lot of things you don't recognize. If you've ever encountered an object, song or movie and wondered, "What on earth is this?" there's a good chance that Firefly could identify it for you.
But when have you ever not known what movie or TV show you were watching? And even then, when have you thought 'I'm going to buy that... or save it to Amazon Instant Video if it luckily appears to be on there'?
The music recognition is good and simple to use, plus the prices generally good on Amazon. But that's basically the only thing to buy this phone for if you're into Firefly, and that's not really a good enough reason.
And of course, like pesky ads in a free game, those little Amazon pop-ups poke you, begging, "BUY ME!"
I'm tempted to say that you can file Dynamic Perspective in the Useless Folder, but such a folder would be ironically living up to its own name.
It's a trick, a gimmick. Sure, it's neat to see stuff move around on your display when you tilt the Fire Phone, and it does give it a little bit of a 3D effect, but it's hardly functional.
Amazon argues that you open up a whole new world of stuff within the display, and you can dive a little deeper into content by peeking around or behind things. But there is absolutely no reason why you need to stuff four front-facing cameras to do this when you can do the same with finger gestures.
It also feels unnatural to tilt the phone around in my hand. I almost want to follow it around with my face, which would defeat the purpose of Dynamic Perspective.
As you can imagine, the degree to which you can tilt the device is very limited - start tilting it too much and your entire perspective is going to be nothing but bezel.
There are a few tricks that Amazon stuffed into Dynamic Perspective. One of those is in maps. If you have several pins or areas of interest that come up in a search, a slight tilt of the phone will reveal the names and/or ratings of each of those places.
Again, most of what you can do with Dynamic Perspective, which isn't much, can really be done with just your fingers. But if this is the best Amazon can come up with to distinguish itself and be unique, it isn't helping much.
Or if you're browsing Amazon - an oddly hard thing to do on the phone - you can tilt left and right to get more information or see a larger picture of the thing you're thinking about buying. It's not intuitive as using your fingers makes more sense... it's akin to 'smart scroll' from Samsung on the Galaxy S4 where you have to tilt your head instead of using the easier fingers.
It's not even that accurate, with the shifting and scrolling juddery and unresponsive. For something that requires FOUR cameras to achieve, it seems a complete waste of time.