No SDK? Point a Stripe webhook at Pagerless instead: several failed payments within 5 minutes wake someone. Details: payments down alerts.
Questions
How do I get alerted when Stripe payments fail in my app?
Report errors from your checkout code and treat payment failures as an outage. Pagerless does this by default: failing Stripe calls are tagged automatically by the Node SDK, and 3 or more payment errors that are at least 2% of payment requests always wake someone with a push, then a call.