A Live GPS task, written by Edan Cain of the ArcGIS Explorer team, has recently been posted on ArcScripts. You can download it directly from the ArcGIS Explorer section of ArcScripts, or by choosing ArcScripts from the Explorer Resource Center.

The task allows you to capture a live GPS location, or optionally start tracking your location based on a specified time interval. The locations are stored as results, and the result popup window displays the XYZ values and time stamp at each location, along with any additional information you may want to add. Other options allow you to dynamically center the map on the GPS position, and change the speed units from kilometers to miles. Additional details can be found in the task summary.

Here's a screenshot showing collected waypoints from a GPS unit, with the popup display showing the time and XYZ location.

And here's the task data tab.