Most listings recommend spot-cleaning or wiping the surface. One cushion specifically advises using a dry towel and warns not to immerse the unit in water.
Some handheld units include a pre-programmed 15-minute auto-off. Other cushions and massage units offer built-in timers, commonly 15- or 30-minute options.
Examples in the listings include: 14" x 6.5" x 6" — 5 pounds; 9.8" x 6.7" x 2.4" — 2 pounds; and 3.41" x 10.23" — 1 pound.