Tiled window switcher
I found Slate which might fit the bill. I've tried out the following ~/.slate and it does directional focus. Will check back after playing with it before selecting this answer.

# Focus Bindings
# NOTE: some of these may *not* work if you have not removed the expose/spaces/mission control bindings
bind right:cmd    focus right
bind left:cmd     focus left
bind up:cmd       focus up
bind down:cmd     focus down
bind up:cmd;alt   focus behind
bind down:cmd;alt focus behind