Visualize this: A woman is pushing a loaded grocery cart through the frozen-food aisle when she gets a mobile phone alert. Her checking account balance has dropped to $100. Uh-oh, the food will be well over that amount.

But wait. Up pops a clickable ad, offering her the chance to sign up - right now - for overdraft protection.

That might be a marketing no-brainer, but it's still wishful thinking in mobile banking. "Banks are starting to ask for this capability," said Drew Sievers, co-founder and CEO of mFoundry, a Larkspur, Calif., technology firm that creates software for mobile banking and mobile payments. "But security risks are a big concern."

Sievers says current mobile marketing strategies have great potential for helping banks gain a greater share of customers' wallets. For one thing, financial services firms can partner with other businesses that want access to their customers, as Visa has done withStarbucks. A mobile gift card application that mFoundry created for Starbucks features a Visa advertisement. Those who use their mobile devices to reload Starbucks cards get an extra $5 added, if they pay with a Visa card.