Sound Activated Tape Recorder
I'd really recommend a sound or voice activated tape recorder. I got a new tape recorder recently. The Sony ICD-UX570. It's set to sound activated (not voice activated, though), so I just start recording when I get to bed, and leave it on for the night. It automatically pauses when it detects silence, and then when it detects sound it automatically starts recording again.
So I can just lay there. When I wake up from a dream, I just lay there. I don't have to move at all, except my lips. I just lay there and speak the dream.
So for 10 hours or so of sleep, the recording ends up being about 30-40 mins. So most of that is semi-silences. But I can play it in PotPlayer at 3x the speed. During the silent moments I write down dream signs from the previous night and stuff.