I think practice drills will be a main benefit
I haven't found any good droid phone BJ aps. There a lots of BJ aps but the ones I found (and paid for) are deficient in one way or another. One had Zen count available, but the graphics and play sucked, and I don't think it could use my personalized indexes. So any training was going to have me adjusting to a different set of indexes, which I definitely do not want to do. Another BJ ap was OK, but if I turned off the screen, it would shut the program off, I found out angrily when I got a chance to turn the screen back on. Several times I didn't get a chance to place those max bets. After that happens a few times, the program is too frustrating to continue playing. Another BJ ap had a pretty nice look and play, but didn't support Zen.
Assuming that there will be various practice drills available in the proposed ap, I have a suggestion for the simple drill of adding up hand totals. Make available the option to have hands displayed that total 21, and also busted hand totals. I think that would be good training for being mentally prepared for some types of dealer errors, like you have a 5 card 21, and the dealer has a 20 and pushes with you. Or the dealer has a 5 card 22 and takes your bet. Right now I'm training on CVBJ, and I was noticing that the "Add up Hands" drill has hand totals that are capped at 20, so I can't get that rapid repetitive drilling of what those 21 and up card configurations look like.
My thoughts on the ideal phone ap: The flashcard drills, with customizable indexes (maybe load on phone with a file?) would be awesome. Drills involving looking at a discard pile are probably not going to be graphically useful, so I'm thinking the phone is not the ideal place for training on discard pile estimation. The Full Table Drills would be nice, and also the Counting Drills. And a realistic full game environment would be awesome as well. What about quick access to all those charts and graphs you've produced over the years? As in, a little reference library. It's probably beyond the scope of a phone to run sims, but maybe a core portion of some canned sims could be accessible somehow? I hope that's not too long of a wish-list.