On battlesuits it allows the pilot of the suit to benefit from a battlesuit support system without it taking up one of the limited hard-points on the battlesuit. Unlike normal hard-pointed versions of the system, it is usually integrated like an item worn by the pilot or a cybernetic-upgrade. However, only Shas'o or Shas'el commanders, Crisis bodyguards, or Shas'vre team leaders are authorised to use wargear such as this.
In the case of infantry, such as fire warriors, hard-wired wargear allows the user to use support systems that normally only battlesuits are able to carry and use. Like above, it is either worn or an implant. Usually only the team leader is authorised to have hard-wired systems.
Types of hard-wired systems
This shows and provides links to all the wargear for the Tau that can be hard-wired for Tau and Fire Warriors. These hard-wired weapon systems are usable by infantry and battlesuits that can take them.