One study found that acupressure wristbands that stimulate a specific point on the wrist can help reduce symptoms of motion sickness such as nausea and vomiting.

Several brands of bands are available. These bands use pressure, electricity, or both to stimulate the P6 acupuncture point ... located about two finger-widths from the crease on the underside of the wrist.

Practitioners of acupuncture and acupressure believe stimulation of this point may stop nausea and vomiting.

The elastic bands usually have a raised surface that applies pressure on the wrist. The bands have no known side effects, so there is no harm in trying them.     - "Acupressure bands for motion sickness"

Adam is well known to suffer from seasickness. In a test rig meant to induce seasickness, Adam lasts about 3.5 minutes. Jamie, Kari and Tory show no signs of trouble, but Grant also gets sick after 10 minutes. With a baseline and two test subjects, it's time for the tests.

Wrist straps: BUSTED. Within 2 minutes, Adam can feel himself getting sick and calls it off; Grant also gets sick, though his time wasn't reported.
- TV.com® (episode 43 of a tv series on the Discovery Channel)

... the P6 acupuncture point located about two finger-widths from the crease on the underside of the wrist. - "Acupressure bands for motion sickness"

This particular point, known as the nei-kuan point, is located on the surface of the forearm, three finger-widths above the crease of the wrist and in the center, between the two flex tendons. - "Seasickness Cure: It's All in the Wrists"

This point is located 2 cun (a Chinese measurement equal to approximately 3 cm) [1.2 inches] proximal to the midpoint of the transverse crease of the wrist between the tendons of palmaris longus and flexor carpi radialis. - "Does Acupressure Help Reduce Nausea and Vomiting in Palliative Care Patients?"

... The P6 point, also known as the Neiguan point or G-Jo point no. 10, is located 2 cun (Chinese inch, equivalent to the width of an individual's thumb) [i.e. 2 thumb-widths] proximal to the distal wrist crease, between the tendons of the palmaris longus and flexor carpi radialis. - "Stimulation of Auricular Acupuncture-Point for C/T-Induced Nausea/Vomiting"