circuit rider

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A cleric who travels from church to church, especially in a rural district.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun An itinerant preacher, especially a Methodist.
• noun US A judge who holds court in a series of towns.
• noun computing A computer consultant who advises non-profit organizations.