[World177]

It looks like the EFF had one. [1] Though, the website currently does not load, and from archive.org, it looks like they killed the project sometime before July 2021. [2]

[1] https://www.eff.org/deeplinks/2016/05/canary-watch-one-year-...

[2] https://web.archive.org/web/20210712025824/https://canarywat...

[kmoser]

We would have known this sooner, if only somebody had built a warrant canary canary canary.

[pacificmint]

At that point, you pretty much have to write it in Java. :)