Spatial armband

The spatial armband is a device created by both Miles Prower and Cobar. When Miles suspected the timeline of being altered, he invented the armband to prevent his family from being erased. Around the same time, Lien-Da forced Cobar to make her an armband before the timeline was altered. (StH: #166)

Five years later, after former King Shadow had been released from suspended animation, he ripped off Lien-Da's armband so that her place in the timeline would change. Argyle is also shown wearing a green version of the armband. (SU: #7)

Background Information
The spactial armband is similar to the spatial stabilizers used by the zone cops.