An autopilot is a mechanical, electrical, or hydraulic system used to guide the vessel using Magnetic Compass or Gyro Compass without assistance from a human being.
Wide Range of Marine Autopilots & Rudder Angle Indicator systems are available from the top brands,

SIMRAD – AP 60, AP70, AP80
http://www.navico-commercial.com/en-US/Products/Autopilots/

JRC – ALPHAPILOT
Comnav – P4  AUTOPILOT COMMERCIAL & YACHT, COMANDER P2, ADMIRAL P3, 1001SERIES, 2001, 2001F, 2001GF, 1420 SERIES, 1440 SERIES, 1460 SERIES
Skipper – ESN200, ESN100