Just under a fortnight ago, we found
that the audio input pins on the iPod touch were indeed active and able to record audio. Now, a modder has constructed a smallish dock appendage that plugs directly into the touch and enables you to input audio. Apparently, the gizmo sports a built-in microphone and pre-amp, which could theoretically be used in VoIP applications or for recording simple voice notes. It seems as though the creator is offering these up to anyone interested, but you'll have to drop him an email to find out how much such an accessory will run you.
, thanks RadicalxEdward]Update:
RadicalxEdward let us know it's going to go for €30 (including US shipping) when it's up for sale, whenever that is.