SMS vs. Apps. Part 1: The System
The first four sections establish the conceptual frame: Why the channel choice is the wrong ask, the causal chain from message-delivered to economic-outcome, the economics of reach.
Part 1: The System
1.1 The False Binary between SMS and Apps
1.2 The Causal Chain for Digital Health Interventions
1.3 Reachability Decay and Economics
1.4 Scaffolding Beats Slick
1.5 Action Beyond Action Beyond the Platform is the Intervention
1.1. The False Binary
Figure 1. The reach-vs-response job-allocation frame.
“Should we build an app or send texts?” frames SMS and app as competing technologies. They are channels for different jobs. A chronic care management program runs many tasks: enrollment, reminders, vital capture, symptom escalation, education, trend tracking. Each has an optimal channel. Sending all of them through a single channel leaves performance on the table. The default single channel is the app, because apps are the venture-backed default.
The operative distinction is reach vs. response. SMS is the channel when reach is the goal; app is the channel when response is the goal. Reach jobs (medication prompts, post-discharge check-ins, appointment confirmations) succeed when the message arrives and the patient acts outside the channel. Response jobs (logging vitals, multi-drug regimen entry, behavior-change modules) succeed only when the patient produces structured input inside the channel. Most chronic care programs contain both kinds of job.
The productive question is which jobs are reach jobs and which are response jobs, not which channel wins.
We’ll go into detail on this distinction in section 2.2, but it’s important to establish here upfront.
1.2. The Operating Stack
Every digital chronic care program runs the same causal chain from message delivered to economic outcome. Each layer is its own measurement object, its own design decision, and its own failure mode.
Figure 2. The Operating Stack — the six-layer causal chain every digital chronic care program runs.
