It's very simple: a flat HTML page for the front end; the back-end is Python on Google App Engine, using Twilio for the text messages and phone calls.
I'm more than open to feedback!
They have their international beta program: http://www.twilio.com/blog/2012/08/twilio-launches-beta-phon... http://www.twilio.com/international
and this page seems to include a LOT of countries: http://www.twilio.com/voice/pricing
But really, if all you're doing is dialing out, then you don't actually need a local number. Just use whatever service you want (us, Twilio, Plivo, someone else, etc) and set the caller ID to a local number or make the call as a blocked caller ID.
To make it more realistic, you should let the call run a bit longer. For example, on my phone with the volume up in a quiet room you can hear the beep when the call ends. With this service the call ends quite abruptly. Perhaps let it run for a few seconds though I am not sure if this would incur any cost on your side?
Seems like I need a much wider image for the BG on mobile devices; I guess this is down to the very high resolution of iPhone screens?
Also, looks like the webfont character in the H! didn't work either.