I can't think of what it is called..
My company wants to put text messages on our phones (7940/7960), in case of outages, or even to wish everyone a happy holidays!
What is that called? System Message? Event message?
The default display on phone shows, Your Current Options. This cannot be customized in Callmanager, but can be done in CME. Now there are third party products that let you show messages through XML (IPCelerate for example). You may want to check with them about the same.
If this is line above the softkey options (Redial, New Call, CFwdALL etc), then yes, this is System Message which is currently only supported on CME.
Incase it covers the entire screen, then it is Idle URL which is support on CallManager. System Message cannot be configured on CM. The Screen will say "Your current options"