Don Juans Have a Secret: the 'Infidelity Phone' Japanese cheaters stick with the Fujitsu F-Series By Neal Colgrass, Newser Staff Posted Jan 13, 2013 5:45 PM CST Updated Jan 13, 2013 5:55 PM CST 9 comments Comments The Fujitsu F-04D cell phone in titanium silver. (YouTube) (Newser) – Japanese philanderers know their weak spot: the smartphone. Afraid that girlfriends and wives will spot incoming calls from certain secret someones, Lotharios in Japan are sticking with Fujitsu's old "F-Series" flip phones, the Wall Street Journal reports. The so-called "infidelity phones" can easily be programmed to conceal calls and texts from particular contacts. "If Tiger Woods had this Japanese feature in his phone, he wouldn't have gotten in trouble," says a Japanese analyst. But with smartphones taking Japan by storm, Fujitsu has added similar privacy features to its new lineup. Like the F-Series, these phones signal users with little changes of the antenna or battery mark. Only problem: they require a separate app. "It's totally useless," says a Japanese blogger who writes about picking up women. US entrepreneur Neal Desai has designed a similar app called Call or Text Eraser that's been downloaded more than 10,000 times—but he cooed when told about the F-Series: "That's more genius than my app," he said.