An interesting post, though it is worth mentioning that there are more fully featured ADCs for doing this sort of thing.
The guys at Zeus have a software traffic manager that you can write rules in Java, Scala and Jython...probably other JVM languages by the look of it. A lot less pain than iRules.
There is an article talking about the way they have written an application that runs on their traffic manager that integrates with the Twilio telephony API.