CardStar offers mobile phone users a simple way to manage physical loyalty and membership cards in a digital manner. Today the service is introducing integration with Foursquare to support check-ins for users of the iPhone application.

Now, when a user scans their club or loyalty card via CardStar during checkout, they can also tap to check in on the location-based service.

The idea behind the integration is to eliminate the extra steps required for CardStar users to check in on Foursquare, and help merchants better verify user check-ins. Additionally, the company hopes to facilitate more engagement between customer and retailer, as well as encourage additional rewards for Foursquare check-ins.

“The typical CardStar user already launches the app at point-of-sale in retail locations, airports, gyms and libraries. The CardStar integration with Foursquare was the next logical step to deliver a more cohesive mobile experience,” says CEO Andy Miller.

The enhanced application also includes a few updates to improve the overall card storage and scanning experience. It has been updated to include support for iOS 4 and now includes a geo-aware favorite places list.

When it comes to the bigger picture, CardStar’s Foursquare integration exemplifies the continued convergence of loyalty programs and location-sharing.

Tasti D-Lite has been very experimental in its integration of social media into its rewards program, even going so far as to build social functionality — which automatically rewards points for tweets and check-ins — into their point-of-sale software. Mobile application Topguest also seeks to turn check-ins into rewards points that can be redeemed at pricey hotels. Of course, many retailers like Starbucks, Ann Taylor, and Domino’s UK are simply turning to Foursquare for a location-based loyalty program that rewards mayorships or check-ins.