Magical items in SR4 all require Karma to be created/bonded (it's one of the required limiting factors of magic in the game).
Also, magic never automatically prevents anything, just gives penalties. As such to have magical items with charges that automatically change targets is more powerful than anything even great dragons have (and they will hunt down this new magic with reckless abandon.... )
Either way, there are already RAW mechanics to make these talismans you want with Anchoring metamagics.
You want it to redirect a gunshot?
You want something like anchored spell with a targeted Control Actions (Trigger, Voice). Force dependent, it will work to control the shooter to hit someone else. Cost? Depends on the force and amount of Karma to be invested in the item (due to the force of the spell), and seeing as karma has no price listed, it's up to the GM to decide how much it is.
The problem here really is that you seem to want more common magic in Shadowrun. Respectfyully, I suggest instead moving to Gamma World, Warhammer 40k or GURPS, as they are much better at making magic a 'common' option that anyone can use.
Shadowrun isn't like that, and there is a standing option from the Draco foundation to invent a magic item that a 'mundane' can use. In your campaign, it sounds like this has already been accomplished, where most GM's still use magic items very, very differently.
For reference though, I love your use of jackets with extra-concealability etc. Just be careful with tracking PC's though, as the more custom items you have in game, the more potential for out-of-the-box abuse and tracking to ensure that Enemies get the same options and advantages. Anything Shadowrunners get, the corps got first