Use of Twilio.com and Salesforce
it is a web-service API for businesses to build scalable, reliable communications apps that make and receive SMS & Phone Calls.
You can use Twilio for below ways:
Lead Generation
Voice Broadcast
Company Phone
IVR
Click-to-call
Voicemail Transcription
You can learn more about Twilio.com and then sign up for a free account to get started. They have really a very good documentation with a lot of sample code with example scenarios to get you up and running.
Salesforce Implementation:
we can implement the twilio and salesforce, see the library files using below links:
https://twilio-salesforce.readthedocs.org/en/latest/index.html
https://twilio-salesforce.readthedocs.org/en/latest/usage/twiml.html
http://twilio-salesforce.readthedocs.org/en/latest/usage/messages.html