iSpellCaster will provide you a complete Enchantments reference for d20System RPG. iSpellCaster is really complete!! It has all core spells (APG, Ultimate Magic included) and more! In fact it contains all spells provided by a lot of Adventure path, and secondary rulebooks.
The app is simple, easy to use, good graphic and there is a great searching system. When you select a spell, you will see the "you could need..." field that contains all related spells, so you can improve your ability to know all about spells that you are looking for.
At this price what are you waiting for?? ;)
Follow me on twitter: gringoireDM