This applet displays a crude map of Oahu with the populations of US Census Bureau blockgroups as scaled rectangles (yuck!) at the blockgroup centroids. When you click on the map, a small black rectangle is plotted there on the map, the longitude and latitude of the place is displayed, and the aggregate travel distance is reported in person-kilometers.
The map is crude, the distances are "as the crow flys" approximations, and the precision of the coordinates is excessive. Still, you may find it fun to try to experiment to locate the "most accessible point" (i.e., the place with the minimum aggregate travel distance) for Oahu's population.