Look for advantage blackjack in the market, im not sure if its free or $1, but anyway its got a counting thing where basically the cards just show up like if u were flipping them over one at a time, and its keeps record of your times. I think like after a deck itll ask u the count. It also has a bs trainer that will tell u if u make any mistakes. Theres tons of normal bj apps out there too, i have yet to find one that helps w/ ace tracking though.
also look for blackjack trainer, i havent really used it, but its another counting app, im just not sure if u can change the counting system from hi-lo.