This app clearly reminds me of the device John McAfee promised us: http://www.theverge.com/2013/9/30/4786008/john-mcafee-d-cent...

"the device [...] has a range of around three blocks. Everyone in those three blocks can then communicate with each other and that will obviously change as users move in and out of a local area."

Will definitively try to maybe see people from HN in Paris.