This is a small mic that fits in the earphone socket of an iPod. (Mine's an iPod Classic). It comes with an overcap that makes it look rather like a bean when closed. When you pull it open you'll see a triple ringed connector that just pops in to the earphone socket.
For the iPhone 3G & iPod Touch you'll need to install additional software, such as iTalk Recorder or Easy Recorder, to use this item. For the iPod Nano & iPod Classic there's pre-loaded software on the units, so you're ready to use this straight away.
Once you put the mic in the iPod, a new menu item appears called "Voice Memos". In there you've a choice of High or Low quality recordings. Just click and start the recording. It'll save the recording as a .WAV file to the iPod. You can make iTunes automatically copy these voice memos to a playlist called "Voice Memos". Pretty simple.
The quality of the recordings are quite good. I tried from a few distances (1, 3 & 6 feet away) and it seemed fine for dictaphone use and even recording a guitar & vocals.
I don't know about how much battery life it drains, as I've not used it for that long as yet. However, as it plugs into the earphone connector, I assume you can plug a charger in to the dock connector at the same time to charge the battery as it runs - which you can't do with a mic that connects to the dock connector. If that works it's a good feature of the unit.
I also like how compact this unit is. It fits on the little bag I've got for my earphones and is very discrete when plugged into the unit.