I have Vonage and was looking into a way of detecting incomming calls and then displaying the CID.
It apepars however that this information is not so readily accessible, however the good old use of a modem apparently is...
Here's a vonage thread about it:
IN this thread it mentions the YAC utility.
This utility runs on your PC and reads the caller ID info from your modem. It then broadcasts it to up to 10 network devices.
So, there are currently listeners for Windows and TiVo. I was thinking of looking into making a listener for the Roku... only problem is I've not done any development for the Roku yet...