As Brian explains, he places the device on top of the dashboard in the cockpit and clicks that he is ok at the beginning and the end of the flight (which is tracked over the internet). Between these periods, the device places him in tracking mode and should something happen during the flight, he can just hit the 911 button prior to attempting an emergency landing.
In addition to explaining how he uses the device on long flights, Brian also provides links to helpful reviews about the device and other similar devices that act as emergency beacons.
The post is well worth reading as all pilots, even those who do not often fly over remote areas, should have such a device on board. Furthermore, such devices are very useful for day to day type of activities such as long car trips and certainly for any type of outdoor activity such as hiking or bicycling. After all, an unexpected emergency can happen at any time or place.