two quick thoughts:

1) can you quicken a preparation when it goes off? i don't see why not if it's using a command trigger. hello, armor fetish! this is what reasonably skilled alchemists would be doing all day, given that the foci market is relatively small next to the "protect rich mundanes from imminent magical manipulation and death" market. price is a bit iffy, but going on at least 2000 nuyen plus given the karma cost. just try not to cross any wards while you're wearing it.

2) for the paranoid VIPs among us: the biofiber executive protection cloak! figure its a wraparound cloak and helmet of about 2 meters of high-force biofiber with an armored exterior. too heavy and bulky for combat, but great for that 30 seconds of critical vulnerability between your limo and your warded building. too ridiculous, or just ridiculous enough to work?