I was really hoping for some concrete app-development lessons learned. For example, was it important to target old/low-end versions of phones? The article both says SMS is a lowest-common-denominator, but also that smartphones are more prevalent than one might assume; what was the outcome from those considerations? I noticed the food stamps app presents one question at a time, with a "Next" button after each one. Was that approach discovered after user testing, or was there just an assumption that that would be more successful for the user base than showing all the prompts on one screen?

Also, I am excited the IT industry has evolved to where these point-solution apps are both easy to build and plentiful. This is the "long tail" in action.

There is a lot of backend infrastructure that enables what I call "UX apps", where 90%+ of the effort is on frontend design and functional requirements, and very little consideration needs to be paid to infrastructure issues like OSes, networking, high availability, etc. The enablers here are things like PaaS, powerful mobile and browser clients, and reliable and prevalent communications (cellular / WiFi).