The iRiver IFP-395.
512M memory, will do voice recording at 96K for some 12 hours. The inbuilt microphone is small, and will give adequate results for recording your own voice and someone you are speaking to in a quiet enviroment. For better results, you'r looking at attaching a couple of external mics. This is all easy to conceal, (the IFP is some 80*25*25mm), if you'r wearing more than a bikini.