In Progressive Railroading magazine there is an ad for Wi-Tronix who has a device that mounts in the cab. It detects placing or answering a cell phone call, the presence of portable Cell based wi-fi hotspot, sending or receiving text messages, emailing updates or browsing the internet via ipad, itablet. In other words, any device emiting in the cellular band is detected, logged and then sent to specified individuals or departments for review.
Big brother is watching.....