Thanks for posting this! The thing I always wonder about with Play and Twilio is if most people use the standard Twilio Java library as you did, or if people use Play's non-blocking WS.url() code and re-create the library?
For our Play 2.3.x Java app, we are probably going to wind up configuring the thread pools to be more like a standard blocking server because we haven't yet found an elegant way to do non-blocking JDBC calls in Java. So a blocking call to Twilio wouldn't make much difference for us. But if we were doing the "one thread per core" setup, then I think I would be worried about using the (presumably blocking) Twilio java library.
Josh