Yowza

An iPhone application that displays coupons offered by local businesses

Reach: 725,000 users
Cost: About $50 a month per business location

MobiQpons

A mobile coupon application for BlackBerrys, iPhones, and Android phones. Coupons are displayed in order of proximity within a 10-mile radius of the customer's location.

Reach: 100,000 users
Cost: $50 to sign up, plus $25 per month per business location

FourSquare

A cell-phone application that lets users broadcast their location to friends. Businesses can offer coupons to frequent patrons.

Reach: 100,000 users
Cost: Free for now, although the company plans to eventually charge for the service

Coupon Sherpa

An application for the iPhone that displays coupons by proximity, category, and brand

Reach: 80,000 users
Cost: Free

Money Mailer

A service that lets companies send text-message coupons when they purchase a direct-mail campaign

Reach: As many customers as you sign up
Cost: $25 to $75 per mailing zone of 10,000 homes

iLoop mobile

A mobile marketing service that sends coupons, quizzes, sweepstakes information, and other offers by text message

Reach: As many customers as you sign up
Cost: $1,500 and up for one campaign or $2,500 a month for ongoing campaigns