I play electric bass, finger plucking exclusively.
My right hand technique seems to benefit from a lot of hard plucking, i.e., practice, practice, practice. I average maybe close to an hour a day practice when I'm not gigging, but I wish I could do more (the wife sometimes asks me if I'm married to her or to my bass ... and I have to think hard about that one

).
Anyways, since my commute time to and from work is a little over an hour, I am looking for a way to work my plucking fingers while I drive (extending the middle finger to rude drivers seems to have little effect). Has anybody figured out a way to do this? I'm even thinking of mounting some old strings to a board with tuners attached to it. Is there anything commercially available?