Google Earth now supports NMEA, GPX

Release notes:

    * Real-time GPS tracking using NMEA (Plus, Pro and [Enterprise])

Major fixes since last beta:

    * Numerous GPS fixes (including GPX import)

Windows and Linux - version 4.0.2693, Mac - version 4.0.2694

This is a major update to the GPS support, which was previously Garmin/Magellan only.
The only option for NMEA support before was to use EarthBridge with a serial interface on Windows, with no option whatsoever on Mac.

It's not being pushed as an automatic update yet, you have to download it (the beta will download by default).

via Google Earth Blog