The mobile phone, which will go on sale this summer, is also able to keep track of each location tested by the user for radiation levels, in order to create a wider picture of Japan’s atomic hot spots.

Masayoshi Son, founder and president of Softbank and an outspoken critic of nuclear power, described how the new phone presented a more portable, affordable and user-friendly alternative to a conventional Geiger counter.

“The threat from the nuclear accident cannot be seen by the human eye and continues to be a concern for many people, especially for mothers with small children,” he said.