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SendiMessage
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Use case

iMessage appointment reminders through one API

Reduce no-shows with timely, clear reminders.

Appointment createdSendiMessage APIManaged lineCustomerCustomer replySigned webhookAppointment system

The business problem

Missed appointments cost time and revenue.

Integration workflow

  1. A booking is created or nears its time
  2. Your scheduler calls the API
  3. Customer receives a reminder
  4. Optional reply handling via webhook

Recommended line setup

One line per region or clinic.

example message“Your appointment is tomorrow at 10:00 AM.”
POST https://api.sendimessage.com/v1/send-message
bash
curl -X POST "https://api.sendimessage.com/v1/send-message" \
  -H "Content-Type: application/json" \
  -H "X-API-Key: $SENDIMESSAGE_API_KEY" \
  -H "X-API-Secret: $SENDIMESSAGE_API_SECRET" \
  -d '{"number":"+15551234567","content":"Your appointment is tomorrow at 10:00 AM.","line_handle":"8eb3ecaf-6487-485d-b01c-b18bdcb57180"}'
201 Created (real response shape)
json
{
  "status": "QUEUED",
  "message_handle": "4e828182-a640-483f-bfe9-17ffcaa51d48",
  "from": "+15555550100",
  "to": "+14155550123",
  "group_id": null,
  "content": "Your appointment is tomorrow at 10:00 AM.",
  "media_url": null,
  "service": null,
  "is_outbound": true,
  "error_message": null,
  "date_created": "2026-08-21T09:07:34+00:00",
  "date_updated": "2026-08-21T09:07:34+00:00",
  "date_sent": null
}

Why a managed line instead of running this yourself

Appointment reminders are time-sensitive and go to real customers, so deliverability and reply-handling matter more than for a one-off blast. SendiMessage operates the line: sends are paced to protect the number's sending reputation, opt-out (STOP) requests are honored automatically, and — where SMS fallback is configured — a reminder that can't reach a recipient over iMessage still goes out as SMS. Your scheduler makes one API call either way; there's no hardware or messaging infrastructure for your team to run.

Frequently asked

Does this replace my scheduling or EHR/booking software?

No. SendiMessage is the messaging layer your scheduler calls into — it sends the reminder and reports what happened. Your booking system stays the source of truth for the appointment itself.

Can a customer reply to confirm or reschedule?

Yes, on a line with incoming messaging enabled. A reply like "Confirmed" or a reschedule request arrives at your endpoint as a signed webhook, so your scheduler can act on it.

What happens if the recipient doesn't have iMessage?

Where SMS fallback is configured on the line, the reminder is delivered as SMS instead, automatically — no separate integration path.

How is this priced?

Per active messaging line, billed monthly — see the pricing page for the current figures and what each line includes.

Ready to set this up?