Wow otter, sounds cool!
I was thinking, you said your mp3 player has voice recording. (Nice to know someone doesn't have a F'ing IPod lol) Depending on how long it can record for you could set it when you go to sleep and then while in your LD try to say to yourself that you will say everything that is happening in your dream IRL. Maybe this would work, maybe not due to sleep paralysis, but hey people talk all the time in their sleep. Try it out and report back if it works, of course put the audio on your computer first or something so you wont have to slowly skip through it all lol. You could try opening it in audacity (recording program) and just skip through until you see the waves go higher indicating that your mp3 player picked up noise.