30 million wearable, wireless monitoring devices were sold in the US in 2012

"Last year, 30 million wearable, wireless monitoring devices—including those used for medical and clinical use—were sold in the U.S., according to ABI Research analyst Jonathan Collins. That figure is up 37% from 2011 and Mr. Collins says he expects sales to rise to 160 million devices a year by 2017."
Source:  WSJ, 8th January 2013
Via Lynette Webb's Interesting Snippets