Knack status badge
Free for anyone. The badge updates every minute and links to the live Knack status page.
Every snippet links to https://damnisitdown.com/status/knack. Options and caching: badge docs.
JSON API
No key needed: GET https://damnisitdown.com/api/v1/status/knack. Cached for 30 seconds; anonymous use is limited to 30 requests a minute per IP. See API docs.