If you looked at the example you will notice two options for the application. GPS device and simulator. Look at the GPS device portion. It will show you how to create a GPS connection, test it to make sure it's working, and set it to a GPS feed. With the GPS feed, you can set it to the realtimefeed in the realtimefeedmanager instead of using the simulated feed.
I know the example is for ArcEngine 9 version and in VB6 but the way to connect to a GPS device, get the feed and display on the map is probably the same in ArcEngine 10. Obviously, I could be wrong since I did this in ArcEngine 9.3.1 but I am willing to bet you can use the same approach in ArcGIS 10.