As stated in Phonecalls:

Now the only thing remained to see how the database is updated with regards to phone calls. It turned out that the number is not visible when the call goes out or comes in (RINGING or OFFHOOK state) but is accessible through the content provider when the IDLE transition event comes in. I was not able, therefore, to capture the number of the currently ongoing call but I was able to capture the number of the call that has just finished.

For a quick and dirty workaround to obtain the number during an incoming or outgoing phone call or sms, using the GSM radio log see Android Radio Logger.

Note that the number of the incoming SMS can also be retrieved in a well-behaving way:

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http://davanum.wordpress.com/2007/12/15/android-listen-for-incoming-sms-messages/
Nice hack, however.

OK, lets talk real-world for a second. Not to sound too cynical, but what do you suppose the likelihood is that when/if
the G-Phone comes out, we will actually be able to capture the data from the phone calls, either real-time or near real-time?

There are significant real-world apps that we would like to create based on this data. Of course, the carriers know this, and are afraid? of making the data accessible. Anyone hazard a guess?

Steve-O