What if there wasn't a [mobile] app for that?

More than a third of small businesses say they couldn't survive, or that it would be a challenge to survive, without mobile apps, says a new survey.

OK, so it was AT&T that conducted the survey—not exactly a disinterested party. But consider that last year, Inc. named the mobile app design industry one of an entrepreneur's best prospects.

The AT&T study found that 72 percent of small businesses used mobile apps in their operations. AT&T surveyed 2,246 small business owners—"small" being defined as between two and 50 employees, both part-time and full-time.

Top on the list of app uses was GPS and mapping, with nearly half (49 percent) of companies using them. A distant second: A tie between social media marketing and document management, with 26 percent of firms apiece. Other popular apps: Location-based services (24 percent), time management (23 percent), travel and expense tracking (22 percent), and mobile credit card payments (20 percent).

The biggest reason for using mobile apps: Saving time, said 62 percent of those polled. Fifty-nine percent cited increased productivity, and 29 percent said cost-saving. (Eleven percent admitted to using mobile apps "to be cool and hip.")

Other survey findings: Small businesses with Facebook pages jumped to 41 percent, from 27 percent in 2009. More than a third of those polled said social media was good for business, with 37 percent saying Facebook et al increased traffic to their company websites.

What do you think are the most essential mobile apps?