YouCompleteMe claims to work with omnifunc-based completion engine, but I couldn't get that to work. Can't tell if it's YCM or foreplay that's dropping the ball, but they don't seem to work together (i.e. I get foreplay completions when I trigger omni completion, but not dynamically via YCM).

EDIT: disregard me, it was a stupid configuration error (both plugins mapped the same key for completion, and foreplay won)