Since 17:52 UTC, every probe runs agent 2.10.0, and the monitor form has six new types. SSH, IMAP, POP3 and FTP are up when the server answers with its greeting, without logging in; IMAP, POP3 and FTP can connect with TLS (993, 995, 990) and then check the certificate too. NTP sends a time request over UDP and reports the stratum and offset. WebSocket is up when the handshake succeeds, and can send a message (verified domains only) and look for a keyword in the reply.
An HTTP monitor can now check a JSON field: a path such as data.items[0].state, a comparison (exists, equals, is not, contains, less than, more than) and a value. A mismatch is an outage with the actual value in the reason, which turns any JSON API into a monitor of what it says, not only whether it answers.
All of them run from every probe city with the usual quorum, at every interval down to 10 seconds, and cost the same credits as other probe checks. The usual ports (21, 22, 110, 123, 143, 990, 993, 995, and 80/443 for WebSocket) need no verification; other ports need a verified domain. Details in Monitor types.