The part in question is the *passive* fob, not the active fob. I wouldn't want to have to use that everyday if the main *active* fob were lost, because it would be a pain in the ass. Meaning, if you lost your main active fob, you are still going to have to cough up hundreds, unless you are OK with messing with the passive fob every time you want to start the bike. That is not for me.
But locked in a safe (or drawer) it would be great insurance against something far worse- losing ALL your fobs (both active and passive), because then you have to replace the entire ECU, and that is a LOT more expensive than fobs/keys...