Getting Remote Computer Status

[sb1920alk]

How do I test if a remote PC is active, locked, logged off, or unreachable (can you distinguish between unreachable, and reachable but shutdown?)?

I'm going to use the result of this test to decide if the script can connect with VNC and log in; connect and unlock; send magic packet, wait (is there a way to re-test every x seconds to see when it's finished booting so I can start the login process?) and login; or if I need to walk over there and check it out the old fashioned way.

Thanks in advance for your ideas.