Example deployment: appointment reminders

The business problem

No-shows cost real money, and phone-call reminders don't scale. Email reminders get opened after the appointment has already been missed.

Recommended architecture

System trigger

A scheduled job (cron, queue worker, or your booking platform's automation) selects appointments in the next 24 hours and sends one clear reminder each. A same-day nudge is optional for high no-show contexts.

SendiMessage API request

curl -sS https://api.sendimessage.com/v1/send-message \
  -H "X-API-Key: $SENDIMESSAGE_KEY" \
  -H "X-API-Secret: $SENDIMESSAGE_SECRET" \
  -H "Content-Type: application/json" \
  -d '{
    "number": "+15555550123",
    "content": "Hi Anna, your appointment is tomorrow at 10:00 AM. Reply YES to confirm.",
    "status_callback": "https://your-endpoint.example.com/status?booking_id=apt_2210&workflow=reminder_24h"
  }'
# → {
#   "status": "QUEUED",
#   "message_handle": "4e828182-a640-483f-bfe9-17ffcaa51d48",
#   "to": "+14155550123",
#   "service": null,
#   "is_outbound": true,
#   "error_message": null,
#   "date_sent": null
# }

Channel behavior and SMS fallback

Reminders read equally well on either channel; "auto" maximizes deliverability. iMessage delivery is available on supported messaging lines and destinations. Recipients without iMessage receive SMS when fallback is configured — never assume universal iMessage availability.

Incoming replies

Your webhook handler applies a simple rule: YES confirms the booking via your scheduling system's API; any other reply creates a staff task with the message text. Delivery events double as an audit trail for no-show disputes.

// "outbound" event → your scheduler endpoint
// Verify the SendiMessage-Signature header (t={timestamp},v1=HMAC-SHA256 of
// "{timestamp}.{raw body}", keyed with your webhook secret), then use
// GET /v2/messages/{message_handle} for authoritative state and match it to
// your booking_id in scheduler.

Messaging-line setup

One line per clinic, location, or region — customers learn to recognize the number.

Security checklist

• API key in server environment variables or a secrets manager — never in client code.
• Webhook signatures verified before any record is updated.
• Only the fields a message needs (phone, first name, reference id) leave your system.

Run the full implementation readiness checklist →

Pricing and managed onboarding

Per active line plus usage. Reminder volume tracks appointment count — bring your monthly booking numbers to the pricing review. Every line goes through managed onboarding: use-case review, test line, credentials delivered securely, and guided production activation.