Network Caller ID (NCID)
Caller ID is defines as "The service that allows someone being called to see the caller's name and phone number." MythTV does not have the capability if displaying Caller ID information, but, with the right tools, this can be made to work.
Displaying Arbitrary Text On The MythTV Screen
As part of the entire MythTV bundle, there is a small script called myth2osd which allows for displaying any kind of text on the screen. Note that this only works when LiveTV, Recordings, or Videos are being displayed; it will not display anything when the menus are up.