Another would be to slow a pulsar's spin down in pretty short order.

ECONOMIST: Pulsars

X-ray millisecond pulsar has proved puzzlingly slow and drawn-out.

ECONOMIST: The dizziest, giddiest stars

But the slow decay in radiation intensity from a tabletop pulsar would make possible extremely long-range transmitters, giving far-off space probes an energy-efficient way to beam information back to earth.

ECONOMIST: Physics