"200 gigabytes/year for audio" is not "still a few generations off" unless you particularly need the device to keep data locally for long periods.
200Gbyte/year is just over half a Gig per day. You could store nearly a fortnight on an 8Gb microsd card (which are not expensive and are very small even with the required read/write interface (see http://www.dealextreme.com/details.dx/sku.25557 for a small one, and this device would not need the physical USB interface so could easily be made smaller)). As long as you switched card or otherwise offloaded the data to other storage in that time your 24/7 recording is good to go - battery life would be much more of a problem than storage.
I can imagine such a device being easy to produced right now. Maybe not as small as a little lapel badge, but certainly "StarTrek TNG broach-like communicator" size or smaller. All you need is a microphone, the card reader, a small processor for compressing the incoming data, and a battery. Battery life would be the big problem, but with advances in processor tech (doing more with less power), battery tech, and the potential in the near future for trickle charging from reclaimed energy (there are a number of research groups showing promising work around gaining power from human movement via devices inlaid in clothes or, for applications such a pace-makers, installed internally) I expect the device you describe is practical in the very near future if it isn't already now.
Heck, I could set my MP3 player to voice record and leave it in my pocket all day. Call that version 1.0, and work on miniaturisation and the interface to non-local storage.