Windows Azure is now supports Telephony and SMS capabilities to the apps hosted in Windows Azure by using the Twilio API. Twilio is a third-party service that provides a cloud-based telephony service which allows to add scalable, reliable voice and text messaging capabilities into you apps. Using Twilio's native libraries for Java, PHP and .NET, developers can build telephony enabled web apps hosted on Windows Azure in which we can make and receive phone calls and SMS messages from phones and web apps. Twillio is providing 1,000 free text messages or 1,000 voice minutes for Windows Azure developers and you can get the free offerings for Windows Azure from here .
Check out the following links for getting more details on Twillio API and working it with Windows Azure