Granny's tweet to grandson got her fame (and a new gig)

Square is an app that allows an iPhone, iPad or Android device to accept credit cards ... and the company's most popular employee is none other than 75-year-old Natalie Yellin from Detroit.

She is also Square developer Brian Grassadonia's grandmother. It all started when Yellin was trying to get in contact with her 30-year-old grandson to plan a family vacation to the Grand Canyon. After weeks of trying to get him on the phone, she finally decided to tweet at him.

She got a user name on Twitter (@GrannyNY) and sent the short message 'B ... call me' to Brian at Square. Brian's co-workers got a real kick out of @GrannyNY's high-tech attempt to reach her grandson, and they put the tweet in the company email.

Another person pounded on his window and made him call his grandma. Soon, everyone was following Natalie. She even became something of a consultant, testing their new product. She is actually a retired periodontist-office financial manager.

Though some have called Brian a 'terrible grandson,' Natalie is quick to defend him.

'He's a wonderful grandson,' she says with a smile. 'He was just busy!'