Digital voice recorder?
Camcorder?
Digital video recorder for TV?
Assuming by your requirement of 2+ day battery life, I'm going to say "Digital voice/audio recorder". There is no such thing as a battery-powered DVR (they're cabled to the wall in almost all cases anyway!), and no camcorder can come remotely close to this.
In terms of audio recorders, Zoom's H1/H2/H4 are very well regarded, not sure about their battery life. You might need to rig up some sort of external power solution like a small deep cycle battery.
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