If Twitter and Facebook app builders were last season’s must have startups, mobile coupon shops are this fall’s Little Black Dress.

Although there are several coupon gurus in the field (cough cough MobiQpons cough cough), I’m a new fan of Yowza(!!).

Seriously, how can you not love a mobile startup with a Heroes star on the founding team? A Mission Impossible and Star Trek alum, Greg Grundberg is no Ashton Kutcher wannabe…

But I digress – back to Yowza. Don’t let yourself be distracted by the cutesy icons and UI – Yowza means business. I’m in big-time-like with any app maker who wants to help me pocket personal ROI using my smartphone.

I downloaded Yowza on my iPhone 3G to kick the tires. Thanks Yowza, at 100% free you’re right in my price range, although I’d probably pay for this app.

For now, Yowza, like many apps, is Appletastic. It can only be installed on iPhones and iPod Touch devices in the U.S. of A.

Although Yowza’s design smells a bit like brand imaging made popular by the laundry detergent crowd (reminded of a Tide box anyone?), I was happy to discover Yowza’s got some bite behind the bark. The app asks my permission for geolocation via a customized message that lets me know exactly what sort of information the company is gathering on me as a user.

I also like the targeting Yowza is doing for my gender and age; I’d rather not get a coupon for a snazzy mens’ store in the Financial District, for example.

After you launch the app, Yowza brings up a nifty map screen with icons from what must be partner companies, including Pier 1 Imports (bleck – did I get this one because I registered as a ‘female?’) and various Rubio’s locations in the San Francisco area and, uh oh, REI stores.

Since I’m hanging at Dealmaker Media in SOMA today, I take note of the fact that Yowza is showing me there’s an REI store less than 5 blocks away at 840 Brannan Street.

After I bring up the map, I tap the ‘star’ icon in the upper right corner of the page and save my 20% off coupon for a discount on “performance food.” With the fall health/tech conference season in full swing, a few dozen Powerbars couldn’t hurt. I can use the Yowza coupon even when I’m not connected to the web, which is extremely nifty.

As I browse other Yowza coupons, I’m starting to regret this download – somehow I have a feeling Yowza will convert me from a casual window shopper to a determined buyer.

What I’d like to see the Yowza team add next: extra featured coupons integrated with email subscription lists to loyalty programs like Sephora.

“Real time” window shopping tours would be particularly useful. I’d like to be able to set the app to ‘browse’ mode when I’m walking home from the CalTrain station after a hard day of meetings on Sand Hill Road and have Yowza lead me to sales I’m wandering past.

Integration with a geolocation update provider like BrightKite or Foursquare would also really get me going.

I’d love to share custom coupons with friends, especially at places where I’ve earned the “Mayor” badge in FourSquare. Imagine sending your FourSquare friends coupons for 20 cents off a large cup of “Ether” blend if you make it to Mayor at Philz Coffee. Now that’s what I call savings built for the mobile life…

It’d certainly be nice to reward friends’ loyalty at communal places of interest and direct them to new undiscovered neighborhood spots via an incentive to save some moolah.

In fact, if shopping is on the calendar, Yowza might make finding a specific store I visit often easier than using Safari + Google Maps or the native mapping client.

Targeted geolocation and locovore-style commerce is definitely on the mobile hot list. Over time, the coupon and loyalty program apps may steal some traffic away from mapping clients – it’ll be an interesting trend to watch.