IPMI generally allows access to the console of a computer by showing the remotely, and allowing remote keyboard (and mouse) movement. This is generally done via some proprietary way, and in most of the machines I've seen, require purchase of an additional license.
IPMI also has the ability to throw a serial console over the network, generally with the
ipmitool sol command.
Several HP servers I've worked with also have the ability to log in via ssh (secure shell), issuing a few simple commands. However, two of the commands connect your ssh session to the console of the computer.
textconsattempts to make a direct connection to the text console (if possible). From here, you can watch (and interact with) the boot process, and, if your system has a text base console, even interact with the running system. However, in most cases this requires you to purchase an additional license.
vspmakes a connection to the running system using a Virtual Serial Port (thus vsp). This bypasses some of the problems with screen resolution issues when textcons may not work.
ssh email@example.com # enter the password for the above vsp # want to watch it boot? Continue below # you are now at the command prompt, open a second shell and log in again ssh firstname.lastname@example.org # enter the password for the above power reset # the second window just issued the command to reboot the server # you can watch the server console during the boot proces