There are several types.
Spotter drones for surveillance and artillery correction. More expensive sensors. Sometimes can deploy other drones.
Grenade dropper drones. They drop several types of grenades. Sometimes several of them. Can be reloaded&reused.
Loitering munitions, basically drone guided artillery munitions. Also there are smaller ones with just grenades. They explode on contact/command. Not reused.
In terms of surveillance. It has been.