Altitude in Google Maps (need help)

It is necessary to fasten to the Google map the ability to show the user a height difference on the route (as here ). Long rummaged in the docks to the API and did not find anything like that (maybe I was looking bad?).
Have any of the habriars faced a similar task? How to at least pull out the altitude parameter for a specific point on the map?
Perhaps there is some kind of service with its api, which distributes such information? I consider the installation of various mapservers last.
Poke, please, nose.