If you need to pay a baby sitter, send money to a kid in college or reimburse a friend for lunch but don't have your checkbook or cash on hand, pick up your smartphone.

An increasing number of banks are rushing to offer or enhance person-to-person money transfer services. In many instances, all you need to send money to someone is their mobile number or email address.

Person-to-person mobile payments are still in their infancy in the United States, with only 4 percent of Web-connected adults using them in 2010, according to a report last month by Forrester Research Inc.