After a short press, you'll see atmospheric pressure and elevation, and your compass position. There are also shortcuts for a stopwatch and for a flashlight. The flashlight app lets you control brightness and blinking, and also has modes to keep the screen on, and to flash out morse code -- it'll even translate your commands into the right sequence.
Slightly customizable, you can easily add other shortcuts into the Activity Zone menu, say S Health or RunKeeper, and call them up with a press of the button and a couple of taps.
Here's the thing, though: If you skip into the settings, you can turn the Active key into a shortcut for almost any app, exercise-related or not.
The only drawback to this Active Key is that it won't work when the screen is locked, which makes it a little less convenient when you're trying to take photos one-handed, like I did a number of times during testing.
Stellar camera and video, reliable performance
Just like the Galaxy S5, the S5 Active has a terrific 16-megapixel camera stuffed with modes and filters, and a video recorder that can shoot UHD video, up to 2160p (though 1080p is still the default). The 2.1-megapixel front-facing camera is also reliable for selfies, and applies a Beauty Face mask by default (though you can adjust it) or turn off the forced airbrushing entirely.
The 2.5GHz quad-core Qualcomm Snapdragon 801 processor is blazing fast and supports rich gaming. Meanwhile, the S5 Active's 2,800mAh battery workhorse keeps ticking hours long, a little over 15 of them in CNET's video runtime test.
Again, my full Galaxy S5 review has all the details, and more photos. But here are a few more, taken on the S5 Active, just for fun.
Strong call quality, fast LTE
The S5 Active was a calling champ when I tested it on AT&T's network in San Francisco. Volume came across loudly on the medium-high level, without much background noise, just a tiny bit of uniform softness to keep it from sounding extra sharp. Voices, though, were warm and natural without any muffling.
My calling partner agreed that clarity and quality both soared. He heard a slight distortion that didn't distract from the conversation, and a subtle frying sound of pink noise in the background that halted when I spoke and picked up maybe a half-second later. Overall, though, I sounded strong and natural, though he said he could tell I was calling from a cell phone and not a wired line.
Samsung Galaxy S5 Active call quality test
Speakerphone was also surprisingly good, without any echo or tinniness on my end that usually plagues this feature. Moreover, instead of sounding thin and distant, his voice sounded whole, complete. The phone did buzz in my hand on louder volumes, and clicked at times (like on the "K" in "OK") when my calling partner spoke. Still, speakerphone was strong enough and reliable enough to use for a conference call and for a call in the car. Likewise on his end, my tester agreed that the speakerphone sounded strong and that he only heard normal amounts of echo from my surroundings.
Just how "Active" is it?
The Galaxy S5 Active occupies a weird in-between place. As far as durable phones go, its reinforced corners rate better than average -- the S5 Active was ding-free after a few drops and after I wedged it into some rough tree branches -- but its slippery backing and lack of grippy material are a letdown in the ruggedness department.
As a phone for sports-minded folks, the convenience key that calls up the compass, barometer, and shortcuts to other apps is useful, but not essential. Since you can quickly reassign the button to open any app, it's good for everyone, and certainly not limited to people with active lifestyles.
Last year's Galaxy S4 Active also had the added advantage of being waterproof, dust-proof and shock-proof where the S4 flagship was not, but that isn't the case with the S5 and S5 Active, as both share these traits.
At the end of the day, the S5 Active gives you a few extra benefits without trading away power and performance. For AT&T customers, the fact that it costs the same as the Galaxy S5 boils this decision down to the handset's physical appearance rather than to its capabilities, which are top notch any way you look at it.