I have no idea where to start so apologies for what might be a vague question. I would like a telephone verification system like elance.com where a user gets a telephone call, and has to either input the numbers displayed on his computer screen, or he has to type in the numbers spoken to him on the phone.
I need this as I want my application to verify that the user is in the UK (and confirm his telephone number at the same time). It sounds simple, I just need an application that will call the user’s number and play an mp3 file (of the spoken code/numbers). But I have no idea where to start. I’ve heard of something called Asterisk, and I have a voip account, but I need the missing links as in how to bring them all together.
Asterisk is the most flexible and powerful option you could use but with your requirements may be a bit of overkill. Asterisk has a diverse range of API options including a thing called FastAGI which lets you pass commands and get messages over a TCP socket. It’s possible to initiate calls and receive DTMF with Asterisk and then pass the result back to your application via FastAGI (or one of the other API options such as curl, pipes etc).
Instead of Asterisk you might be able to use one of the voice application platforms and save you the very large effort of setting up your own Asterisk server. Ones that I know of are TringMe, Tropo and Tellme.
It’s also worth noting that if you are planning on relying on the fact that your users have a UK number that they are in the UK you will be taking a big risk. It’s trivial to get a UK phone number and have it directed to a VoIP phone anywhere on the internet.
Update: Twilio is another one.