Tararua Eyebright or Euphrasia drucei.

These little herb plants grow on mostly on the shady sides of the banks of the roads around some of the Sounds. Spotted a few of these today, and here it is.
Found in damp herbfields, fellfields, subalpine scrub, damp, rocky places and alongside streamsides up to 1,550m altitude, throughout the North Island and as far South as North Canterbury." (from J. T. Salmon's book Native New Zealand Flowering Plants.