Isolinear tags are devices used by the Son'a's drones to circumvent the transport inhibitors deployed by the Enterprise crew to prevent transport. They appear to be weaponized versions of transporter armbands, delivered by drone aircraft with dart launchers.
Isolinear Tag Usage
Small and easily fired into targets, the tags proved to be very useful in beaming up uncooperative personnel. They have the added benefit of linking to the transporter system to initiate transport as soon as a target is hit, preventing the person from removing the tag before transport can occur.