Peter, I'd like to try the current version (iPhone OS7) just for use at home on my simulator, where there are no noise issues. And for calm days when I am flying without a glow engine nearby. I've registered on TestFlight.
I'm also a Jeti user, and also wrote to them about adding a caller-like function to the Jeti program.
What about making an extension for the headphone cable? Then hack into the wire for the microphone or the in-line switches. Connect that to a switch that's mounted on the transmitter. There must be a way to read the result programmatically, the same way that the music player reads the switches on the headphone cable.
Just for interest, here is an alternate virtual caller solution from user WildPalms on RCGroups:
I took a spare Jeti R5i short range receiver, connected it to an Arduino microcontroller and read the signal (pulsewidth) from one of the channels. The Arduino then talks to a Sparkfun MP3 trigger board (using a serial link) that has all the manoeuvres on a microSD card. Flicking a momentary switch on the TX causes the Arduino to demand playback of the next manoeuvre MP3. I can also use the TX side slider to determine if that would be next, last or repeat.
He told me he was going to make version 2 on Raspbery Pi. Very cool, but the smartphone solution is much more elegant, to my mind.
David