I used a voice-activated recorder (Sony), that I bought at Circuit City for about $70. It has USB capability by which you could easily offload its contents to your laptop, then erase it, replace the batteries, and re-deploy it.
I didn't have too much trouble with road noise The times my wife put the car radio on, it would drown out her conversation with OM, and then Florida afternoon thunderstorms would also set it off. But for the most part, it worked flawlessly.
