These technically gifted zealots provide the Unity with the necessary acumen to maintain its myriad of pre-War devices, from the Vault computers to the Vats control systems. They are universally fanatical and completely indoctrinated into the Unity to the point where they would commit suicide if either the Lieutenant or the Master died.
They serve little purpose other than flavor. If attacked, they will retaliate, but generally, they leave the player alone. In case he killed the Lieutenant, then techies in Mariposa will commit graphic suicide, exploding into fleshy giblets.