Check out InformaCast from Berbee http://phone-xml.berbee.com/
I am pretty jazzed about their product. It provides both text and audio messages to the 7940/60 phones. The audio is way cool. You can send an audio message to any number of phones and it will auto-answer the speaker and play the message. If the phone is in use, then the message is blended into the handset/headset/speaker and only the IP phone user can hear the message. The IP phone user has the option to stop the audio message.
Berbee offers a free trial download and I think it is priced to sell to everyone.
