Chess Openings Wizard (downloadable software; no mobile app... in the process of developing a mobile app for the past few years).
Chess Positions Trainer (downloadable software, not regularly maintained from what I have heard).
There are some other lesser known mobile apps for opening training, but the couple that I have seen give you a repertoire to drill, rather than you being able to create, input, and train your own.
Is there a good mobile app or maybe website for drilling a user created opening plan?