I tried an experiment with my iPod running iPodLinux last night. I stopped by Wal*Mart and picked up a Cheap Ass AudioConferencing Headset 3000â„¢ (for a whopping $19.95), came home and rebooted my iPod into iPodLinux. I set the recording sample rate to 33KHz and tried recording a few things to test it out. Worked well enough. But don't try to playback the files under iPodLinux - it will crash.
Also, while recording, it seems to record the file to disk every 5 seconds, with an audio electronic feedback hum while it's doing it (it only lasts for about half a second, but it's quite annoying). I wound up recording about 45 minutes of nothing, just to see if it would crap out on a long recording. Turns out, since it's recording to disk every 5 seconds, that it isn't the bestest thing you can do to your iPod's battery... Although the linux side was showing full battery strength, when I rebooted back into the Apple iPod OS, the battery was showing almost no juice left. I wasn't too worried, since it often shows little juice, but "warms up" or calibrates or something over a few minutes to show the actual level.