The following sources were cited in SAP Digital Futures Issue 12 Making Sense of Sensors

Experts predict there will be up to 10 trillion sensors by 2025.
Janusz Bryzek, “Roadmap for the Trillion Sensor Universe,” (PowerPoint deck, slide 13), Gilt Tech, November 26, 2013,

Image, speech, and voice recognition are advancing quickly and may soon surpass human abilities.
John Markoff, “Researchers Announce Advance in Image-Recognition Software,” The New York Times, November 17, 2014,

“The Revolutionary Technique that Quietly Changed Machine Vision Forever,” MIT Technology Review, September 9, 2014,

Robert McMillan, “Speech Recognition Gets Conversational,” Wall Street Journal – Digits, May 28, 2015,

The cost of passive RFID tags ranges from US$0.07 to $0.15 today and continues to fall.
“RFID Frequently Asked Question,” RFID Journal, accessed December 22, 2015,

The Internet of Everything market could grow to $14.4 trillion by 2022.
Bradley, Joseph, Joel Barbier, and Doug Handler, “Embracing the Internet of Everything to Capture Your Share of $14.4 Trillion,” Cisco Systems, Inc., 2013,