Wow. That is interesting. I am not aware of any Cisco developed tool that will do this for you. You have to look in at least two places for the data. You would need to look at CDRs to determine calls that are placed, when they were placed, and duration. You would also need call manager service traces to correlate key strokes. This assumes you are using SCCP and that the traces are set to Significant level. You need that to get the kpbutton trace entries.
The CM traces would also show the calls that users initiated as well. There may be a 3rd party tool floating around or you may be able to develop your own tool. You would need to get your CM traces off box using a scheduled process of some type (later revisions of RTMT can schedule retreival of traces, but I haven't used it heavily).
HTH.
Regards,
Bill