"Mommy, what's an Icelandic incest-blocker?"

"Well, sweetheart, if you listened to QI podcast #25, you would know that there is an app that informs Icelanders how closely related they are to a new acquaintance.  Additional details are available at the Icelandic Grapevine."

...two random Icelanders have about as much in common as second cousins, once removed, according to Dr. Kári Stefansson, CEO and co-founder of deCODE Genetics...

In early 2013, deCODE Genetics and the University of Iceland’s School of Engineering and Natural Sciences challenged the nation’s university students to design a smart phone app for the online genealogical database Íslendingabók for its 10th anniversary.

The Íslendingabók website takes its name from the Book of Icelanders, a 12th century historical text which details the Icelandic settlement. Currently, the database contains 810,000 genealogical records of “the inhabitants of Iceland, dating more than 1,200 years back.”..

...one of the novelty features of the winning ÍslendingaApp: the Sifjaspellspillir or “Incest Spoiler” alarm which alerts a user if the person she plans on going home with is a near relation. Using the app’s “new bömp technology,” users can tap their phones together and see how closely they are related. If the alarm has been activated—it’s turned off in default settings—it will either erupt with a discouraging siren, or issue a gleeful “No relation: go for it!” message...