[GPSNavX]

Not much I can do about the mail interface constraints you list, but as far as the chart scrolling back to the GPS position this is an easy setting change. By default iNavX will scroll back to your GPS position, but simply selecting "Pos. Icon Kept Visible" to "OFF" in the Chart "Setup" this behavior is disabled. In the event returning the chart to the GPS position is desired, simply tap the "Chart" tab a second time.

http://www.gpsnavx.com/iNavX/help/usingcharts.htm