What the urge to move actually feels like is something members often describe in their posts. I don't know whether anyone has attempt to classify them according to the type of sensation - electric currenty, tooth-achey - and by location - buttocks, upper arms, feet - and if the sensations differ according to location. But it seems to me it would be useful. Perhaps it's already been done.
What did strike me after reading flailingman's post on sensory distractions the other day - watching a movie - is that while RLS is clearly somatic it is clearly psychological as well. There appears to be a growing belief nowadays - underpinned experimentally - in a strong link between behaviour and cognition and the physical brain and nervous system.
Then I thought that if this includes the spinal cord, then there may be a system of sympathetic reactions to a changing environment in and around the spinal cord, different pressures for example, tiredness. By sympathetic I mean a cause in one part of the nervous system creating a sensation elsewhere.
I know this from personal experience in a way. I went to a reflexologist last autumn, just to give it a try, and during the sessions pressures on different parts of the foot resulted in RLS urges (the electrical, tooth-achey kind) which stopped when she stopped working on that particular part of the foot. What if RLS is really a back problem? (That's a serious and dopey question at the same time.)
Anyway, just thought I'd throw the idea out.