Remember the good old days of DOS, when you could open command.com with a simple text editor and find the line with the dreaded "Abort, Retry, Fail" message.
Unwary users were so supprised to see "You're F!*%ed" or some such. And no ammount of rebooting would solve the problem.
Using various slices of the RF spectrum for sensing rather than communications has fascinating potential and some impressive implementations, but there are still many significant challenges, especially in the terahertz (sub-mm) band.
Using environmental energy to power remote sensor nodes remains a high interest item among system designers, especially those choosing wireless sensor node (WSN) components for remote and/or hazardous locations. At the Sensor Expo conference in Santa Clara, Calif., presenters at an energy harvesting and power symposium agreed that energy harvesting systems still require juggling many variables.