(CNN) -- Talk about a "smart" phone—Japan's latest mobile phone sensation also happens to be a radiation detector.
The Pantone 5 107SH is the world's first mobile phone with a built-in radiation sensor, merging phone technology with a pocket Geiger counter, the company says.
Softbank spokeswoman Natsuko Kameda says the company's CEO decided to launch the phone after customers sent messages via Twitter asking him to develop the handy product in the wake of the 2011 Fukushima nuclear disaster.
Many of the messages, says Kameda, were from mothers with young children.
"This device will allow people to measure radiation everyday, wherever they go. People always have their mobile phones in their pocket," Kameda said. "If you have this radiation reading device in the cell phone, then they can check radiation at any time and it should help lower anxiety."
On first blush, the phone looks so ordinary that it's impossible to tell there's a radiation meter within. Softbank said the meter is small so it doesn't enlarge the device. For that reason, the radiation readings are not as accurate as larger, medical radiation readers and dosimeters. But tests so far show its mobile phone radiation reader rivals current consumer brands on the market, Softbank said.
The phone also allows the user to compare radiation readings with radiation maps available on the web.
Japan has seen a skyrocketing demand for dosimeters and radiation monitors since the Fukushima disaster. Citizens fearful of radiation spreading through the food chain and the air have been buying meters.
Softbank says the phone will be available in mid-June.
Softbank is led by CEO Masayoshi Son, a well-known opponent of nuclear power. He has publicly supported solar farms as a replacement for nuclear energy.