Getting phone number in vxml

I am trying to dynamically capture the phone number being dialed. Is there any session variables I can reference via the vxml? Please advise on how to proceed.

No.

But it should not be a big deal to get it. In your call request, you can set the phone number in your starturl as part of the parameters. For example,

starturl = http://mydomain.com/myurl?phonenumber=1234567

When the call is started, it will invoke the starturl and your app should be able to get it dynamically.