Location-based services allow you to report your current location in real time to a given platform. This is usually done by checking into locations -- such as restaurants, retail shops, airports -- manually from a smartphone. Inevitably such services will become more sophisticated as GPS data improves, allowing you to track your movements and checking you into locations automatically.

Foursquare, probably the best-known dedicated location-based service, topped 10 million users this week, handling about 3 million user check-ins daily. While it has yet to turn a profit, it recently raised $20 million in funding at a valuation of $100 million. Meanwhile, the company announced a deal with American Express on Thursday that offers discounts to credit card holders for linking their cards with their Foursquare accounts. In a test deal earlier this year in Austin, Texas, users reportedly spent an average of 20 percent more at local businesses.


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