howto use nc or ncat to "ping" a remote host on port 22 ssh (would work on any port, really) and get a "Yes, this host is online"/

A chat server written in go that implements ssh. SSH to the box in question and it drops you into a simple IRC-like chat. Your username in chat is your username on the machine you're SSHing in from.

Fabric is a Python module which lets you write scripts in Python that carry out just about any administrative task you might need to carry out without having to fuss with os.shell(), .popen(), or anything else. SSH's into a system (even localhost) and does what you tell it to.