My wife has taken a CaneMaster seminar (
www.canemaster.com) and has been practicing with a hickory cane. She's getting pretty good - tripping and whacking me like Kato attacking Clouseau in The Pink Panther. I'm safer on the streets!
I have trained with the Tonfa - the martial arts predicessor of the PR-24, but you can carry those (or a Bo, Naginate, Sword, etc.) around without attracting attention. I figure a baton would be a reasonable impact weapon to carry if I can do so in a less overt manner.
BRET