In-App OmniFocus Pro purchase

I have the ability to purchase the In-App Pro upgrade for my Mac OS X but not on IOS, if I purchase that, will the extra pro capability work on my IOS8 phone or iPad versions?

Pro upgrade is available only on the iPad version. In a recent Omni announcement, it is said that the iPad will become a Universal app - you can use it on both iPad and iPhone. If you have the iPhone version, you will not get the option for in-app purchase of pro features.

The Pro in-app purchases on Mac and iPad are independent. If you want to (say) edit perspectives on both platforms, you need to purchase both Pro in-app purchases.