I have tried three different apps 1. Iconfess, 2. Mea Culpa, 3. Confession. They are all about the same, they have Examination of Conscience and different appropriate prayers for use during Confession, and give you a handy list to read off to the priest. They are all also password protected so no one can sneak a look.
The main thing to remember when using these apps is that they are only meant to be an aid to “jog” your memory for mortal sins and other sins that you may otherwise have forgotten, and not replace the Sacrament itself.
But of the three I have used I would definitely recommend the third one called simply “Confession”. By Little i Apps. It will customize your Examination to your age and sex, (the other two have just have a “one size fits all” approach. I also like the overall appearance and function of this one over the others.
Good Luck!