Chronal accelerator

The chronal accelerator (a.k.a. chronal harness) is a device created by Winston for Tracer. It counteracts the effects of the chronal disassociation she suffered, keeping her anchored in the present. In addition, it gave Tracer the ability to control her own time, allowing her to speed it up and slow it down at will.

The accelerator temporarily gave out on at least one occasion, robbing Tracer of her abilities, but still keeping her in the present. When it was destroyed when Tracer was battling Doomfist, she began to blink uncontrollably (the device was presumably fixed or repaired afterwards).

Sombra's translocator appears to use similar technology to this device, and it's suggested Sombra stole it.

The chronal accelerator can be taken off and still keep Tracer in the present as long as it is on and she is near it.