otp-watch

Your login sends a code by SMS or email. Your uptime monitor says the API returned 200 — but a carrier filter or a blocked sender domain means a chunk of users never get the code, and you find out from a support ticket. otp-watch is synthetic monitoring for that gap: it hands you a real number or a disposable inbox, you trigger your own verification send to it on a schedule, and it tells you "received" (with latency) or "timed out". Email checks are free, no signup; SMS monitors are €29/mo.