Overview
The QGIS Elevation Plugin obtains point elevations using the Google Maps Elevation Service and displays them in Google Maps.
Requirements
Use of the extension requires acceptance of the Google Maps API Terms of Service
It's a QGIS plugin, so Quantum GIS is required.
Installation
The QGIS Elevation Plugin can be installed from the QGIS User-Contributed Python Plugin Repository.
Example map
Source Code
The source code: elevation.zip
The QGIS Elevation Plugin is open source software, released under the terms of the GPL.