New resco Audio recorder supports automatic monitoring of phone calls and record it in back ground. Though WM5 / WM6 hardware do not support call recording like PALM / Symbian I got simple solution.
1. Take original wired hands free kit.
2. Drill small hole in plastic case opposite to microphone hole
3. Stick one ear pod on this hole. Before than make small tube so that sound is directed properly mo microphone.
4. Adjust your Resco Audio recorder to record calls.
I will say I get about 70% of quality than native hardware supported phone. It is better than nothing at all.
Download latest Resco Audio recorder from
http://www.resco.net/pocketpc/audiorecorder/default.asp
See this photo for call recording setting
Also download Audio file if you want to check how opposite party is recorded.