Callum grew up playing soccer in Kailua, Hawaii for the Volcanos before moving to the Mililani Strikers. He played 4 years at Punahou High School and was named NSCAA All-Region. In 2004, Callum was named All-American by NSCAA and was the 2004 Hawaii State Player of the Year. Callum played Division 1 soccer at St. Mary's College in California before completing his degree at the University of Denver.

Callum began his coaching career when he came back to Hawaii to work and help coach the Honolulu City Football Club while playing Division 1 MISO soccer for Lanikai Tuesday. Callum currently holds the title as the Director of Coaching for ALBION SC Hawaii in Oahu, and possesses a USSF "C" coaching license.