Cas it would be no different than a battery. as long as ya keeps yer dick skinners away from where they don't belong, ya should be fine!
Seriously though, it'd be just as insulated, and protected and protecting as any battery would to keep itself, the bike, and you safe.
Lets say that you did get into a catastrophic wreck. With a battery, it's chemical, so it's generating electric as long as the chemical action is going on, so in theory could possibly keep making electricity and fire for well... several minutes after the event, depending on how fast it finally all burns through, being a threat for that entire length of time. With a capacitor ALL the electricity is already there, stored as an electrostatic field. When it goes, it all goes at once, you'll get the blow out, then it's over, it's all used up, no chemicals making more electric, to continue the power hazard.
With this in mind, one could say that capacitors may even be safer.
Just make sure when you set it off, you are below 88mph.
Aaron