Mac App to do simultaneous sound record and playback.

Hi,

I am looking for an application for my MBP (preferably OS X application, though windows would be ok as well) for the following:

I want to be able to record my phone conversations on MBP when using my phone.
My Phone provides me a speakerphone for sound input(my voice) and sends sound output(other party's voice) into a standard 3mm pin which I can connect to Line-In of MBP and record sound using any normal voice recorder.
But I also want to be able to simultaneously hear what the other person is saying so as to respond to him.

Which application can I use to do simultaneous record and playback of the Sound entering into macbook-pro's Line-in jack??

Searched internet for this, but what I cud come across, did not help much.

Hopefully I am making sense, and if any doubts in understanding problem just shoot ur question...

Any DAW (such as cubase/logic) can do this. I suggest you look at reaper. It's a ridiculously cheap application, about £40 for the personal license (and the free demo version is fully featured). Should be more than good enough for what you want to do.

Also, Reaper atm is a full program in windows and beta in OSX, I've been using the OSX beta since switching to mac and logic for a few programs and it works absolutely fine.