Google phone manager - a threat to telecom companies

Google Voice, which will be available to the general public in a few weeks, will allow you to use one phone number and redirect all calls from it to your home, work and mobile phones at the same time.
A useful feature would be a single control center for all your voicemail.

An important difference from Skype, Google Voice users will have access to their voicemail from a regular phone. And from there you can dial any number.

Google Voice allows you to make free calls within the United States, and quite cheaply in other countries.
For international calls to landline phones, Google Voice is generally cheaper than Skype, and for calls to mobile almost a third.
At the same time, there will be no advertising in the service. Significant savings came from switching to google servers (previously, the capacities of the company founder GrandCentral were used).

source in English.