Point Nightbell at a URL, one element on a rendered web page, a Prometheus server, your service's own health report, a GitHub repository, a host by ping or TCP port, or an IMAP mailbox, and it watches it, charts it, and gets loud when it breaks. There is no server and no account. The phone in your pocket does the checking, and your API tokens and target URLs never leave the device. Nine kinds of monitor: - Status check: hit a URL, assert on the status code. - Request and response: pick the method, set headers and a body, assert on what comes back (contains, equals, regex, or a JSON field by path). - Page element: load the real page in an embedded browser and watch DOM nodes you picked by tapping them. - Prometheus: read a metrics endpoint, run a PromQL query, or watch Alertmanager. - Health endpoint: read the report a service writes about itself, part by part. - GitHub repository: stars, issues, pull requests, comments, releases and downloads. - Ping: ICMP echo over IPv4 or IPv6, no root. - TCP port: connect to one port and hang up. - Mailbox: new mail in an IMAP folder, louder for the senders that matter. Urgent alerts arrive as a full-screen red page with a looping alarm that keeps going until you acknowledge it, and it wakes the screen even if the phone is locked. A first-launch screen walks through the four Android grants a paging app actually needs (notifications, unrestricted battery, full-screen intent, Do Not Disturb access), because two of them have no system dialog and have to be opened by hand. A home-screen widget shows the worst monitor first. Settings let you shape the alert policy: what counts as down, sound, haptics, escalation, and quiet hours. Signed with the developer's own key. No Play Store listing.