Signl4

Signl4 is an alerting service, capable of sms/phone/mail/push-notification alerts, and managing oncall rotations.
The free tier supports unlimited push notifications.

Documentation

home	https://www.signl4.com/
signl4 webhook docs	https://connect.signl4.com/webhook/docs/index.html

Setup

- download the app (no web dashboard)
- from app, can configure "critical alerts" that get pushed during "do not disturb", when phone is slient