Just had to share because I've tried tons of TTC apps with opk tracking and didn't like them so I tried OPK specific apps if anyone is interested these two are my favorites:

Premom is great if you want to take pictures and see them stacked together for easy comparison and tracking.

Fertility Tes Analyzer is really accurate with telling you whether the test is positive or not, it actually gives it a percent positive score then it will chart those to show you the surge as well and you can compare cycles too. It does take a bit to figure out though not as user friendly as some other apps!