SoftBank's Pantone 5 107SH will make headlines in the global press for one reason and one reason only — it's the first phone in the world to come with a built-in radiation detector — but it'd be a big deal in Japan even without that headline feature. Indeed, SoftBank CEO Masayoshi Son introduced the Pantone 5 onstage today without even letting the audience know what that color-matched button was for, and showed off a new commercial that makes no mention of the functionality at all. The carrier's colorful range of Pantone phones has long been a hit in its home market, and a first smartphone entry for the series running Android 4.0 is almost guaranteed to make a splash.

The Pantone 5 is a fairly middling device on paper, with an 3.7-inch 854 x 480 LCD, a 4-megapixel camera, and a 1.4GHz processor, along with the obligatory 1seg TV tuner, waterproofing, and infrared data port. While it's a fairly unimpressive 12mm thick, it feels well-built and the design is very much in line with the pleasingly chunky nature of other Pantone phones. You can take your pick from eight colors, with the purple and teal being particularly fetching. As for software, by default it's running the same Sharp skin that we saw on KDDI's Aquos Phone Serie. We still can't say we're fans of the iOS-style approach to Android 4.0, but it does at least look a little more attractive on a smaller screen.

Despite SoftBank relegating its inclusion to a separate section of the press conference, the radiation detector isn't exactly tucked away on the device itself; the Pantone 5 only has one physical button on its front, it's the same color as the back of the device, and its sole function is to open the radiation detector app. The app itself is incredibly simple — press the button, wait ten seconds for the detector to acquire a reading, and then see how many microsieverts are flying through the air. SoftBank claims that it'll be accurate to within 20 percent, and doesn't recommend its use in critical situations. Still, it should be able to provide a ballpark figure for anyone concerned about their environs.

What we can't quite understand is why such a left field feature has been put front and center on an attractive mainstream product that likely wouldn't have needed the attention boost. Whatever SoftBank's noble safety concerns may be, it's simply not a feature that is going to be accessed enough by most to justify its own button, and if anything it could arguably further stir the anxiety that many Japanese people have felt since last year's Fukushima disaster. Still, it's a differentiator for the device if ever we've seen one, and there's clearly a market for it — Apple stores in Japan have been selling iPhone-compatible radiation detectors for a while now. We'll have to see if the Pantone 5 proves a trendsetter once it's launched towards the end of July.