that's called "security through obscurity". and sometimes it works great! Well, the first time. Of course, just like the shoe bomber changed airport security

that's called "security through obscurity". and sometimes it works great! Well, the first time. Of course, just like the shoe bomber changed airport security forever, an rfid keyfob like you suggested becoming commonplace, would just lead to the cops immediately tazing and tackling you, and treating every single motion of your arms as an attempt to destroy evidence.