Wondering if you have considered adding Pushover or Notify My Android support to MM. I haven't messed with either API all that much, but I think Pushover has some response functionality, and they both have various notification priorities that can be set. I also notice that Pushover has added a group functionality so that groups of people can be notified with a single API call. There could be some interesting fail-over to Twilio functionality too. Just wondering...
I suppose Pushover would be the better choice since it is available for iOS and Android. One thing that I like about NMA is that it integrates well with Tasker and FireAlert on the Android side of things.
JL