I'll second the IZ2UUF app. I use it on my tablet, and it's pretty good. I'm about 75% thru using the G4FON character sequence and have had better success with this than any of the several other schemes that I've tried. Another good one that I recently found is called "code practice" (it is free also by the way) similar to the IZ2UUF, but the timing between hearing the sounds and when the character is displayed is better. I like to try to say or write the letter before it's shown with this app, where there is just the slightest delay. I like the reinforcement of hear it/say it/see it. The IZ2UUF app actually displays the character while it's sounding it out. I have the added hurdle of having learned Morse code the wrong way to pass the Novice/Tech 5wpm back in the day, so having to "unlearn" and control the urge to count dots/dashes. The numbers are rough for me. You're right about some of the other apps. they aren't even "toy" quality and are evidently written so that their authors can say that they have written and published apps.?? You are on the right track-Learn it right the first time!!!