While not a "gadget" per se, the Batmobile is one of the most important tools Batman has at his disposal. AND, it just so happens that it can be summoned via his utility belt.
In fact, this ability was a key mechanic in the Batman: Arkham Knight game, also though, Batman has had need for his car in key siutations, so he'll summon it with a push of a button.
The Batmobile is near indestructible depending on which version it is. It's armed to the teeth, and protects Batman from numerous dangers. If the car comes your way? Do yourself a favor. RUN!