it's technically very easy. In fact RIM developpers did the opposite : the feature was available and they blocked it on purpose. The reason is that there are some legal issues with recording someone without them knowing that.
It's the same as the BEEP sound when you take a picture : it's something that was added.
The search box on top-right of this page is your true friend, and the public Knowledge Base too:
Bummer that is seems to be a scam. I just posted elsewhere that I am looking everywhere for a way to record phone interviews on my blackberry (I am a reporter). If I can do this I can get rid of my $60/month land line. I'd happily take a radioshack gadget but none of them seem to work on Blackberries either. If anyone knows of anything that works, would love to hear it!
Has anyone tried mVoice by MotionApps? Just discovered that QmobilSoft makes the exact product, known as CallRec, but for the Palm! If only they (or someone else) made it for Blackberry. Any other developments?
Totally maddening. Am now seriously considering ditching the Blackberry 8220 and getting the new Palm Pre. Such a shame. But I really do need this feature. A pity it has proved so difficult for RIM to make it accessible. Thanks for all of your help!