Using in production: Rollbar (error monitoring), Hyperping (uptime monitoring), Cloudinary (assets management), PushMore (notifications on Telegram of stuff), Mixpanel (action tracking) & Drift (customer live chat).

For #apercite, we use : Drift (live chat), UptimeRobot (status page), Sentry (error monitoring), CloudFront (CDN). We also have Prometheus+Alertmanager+Grafana for internal monitoring, although we host it ourselves. Slack is our communication central, most of those tools post messages in channels there if anything requires our attention.