Also, not exactly what you asked for, but rather than embedding your telnet shell in the presentation you could make the command prompt window "always on top" using a variety of tools. When you get to the point of your presentation for telnet, you could ALT + Tab to bring it up.
CMDOW Commandline Window Utility is a utility that allows windows to be listed, moved, resized, renamed, hidden/unhidden, disabled/enabled, minimized, maximized, restored, activated/inactivated, closed, killed and more. It has a /TOP switch that makes the specified window always on top. Perhaps you could use it to automatically trigger your telnet window to appear on top and at the position and size you wish at a certain point in the presentation.
Console is a free command prompt replacement that has an option to make the window always on top.
JPSoftware's Take Command is a paid command prompt replacement that has an always on top option.