New bank apps promise fast money transfers between you and your pals. But you may still want to carry cash.

Banks' latest push: convincing consumers that shared taxi fares, split restaurant checks and other personal cash transactions are better handled via a smartphone than by handing over a few crisp bills.

A growing number of person-to-person (or P2P) money transfer apps for smartphones and tablets promise to quickly move money from your checking account to a friend's, or vice versa. There's no need to share account details with each other, the app designers say -- all you need is the friend's cellphone number or email address. And in at least some cases, it's free. Bank of America in late July became the latest bank to join the party, announcing that it was enhancing its apps to allow mobile transfers through a processing network called clearXchange, which is jointly-owned by Bank of America, Wells Fargo, and Chase.