Morse Me! is morse code practice tool. It is based on "Koch Method" which basically trains your brain to hear morse code on normal CW speed and pace.
One of the most suggested tip in practicing is just listen, listen listen. Just leave this app playing - It is basically grinding the letters to your brain.
You pick the characters you want to train and just enable playing. The app will repeat the characters either in random order or in sequence and you can leave this app running in background for example while you drive, walk, cook etc. and let your brain adapt to the morse code.
Also features speech option where the app speaks each letter - great for practicing without looking at your phone.