Foursquare location service adds comment, photos

Foursquare, a popular location-sharing service for smart phones, is now letting you upload a photo of that tasty burger you're about to bite into. You can also let your friend know, through a comment on his recent check-in at a bar around the corner, that you'll meet him when you're done chowing down.

Photos that you upload with check-ins will only be viewable by your friends on Foursquare and other social networks with which you share your Foursquare data. Those could include Facebook and Twitter.

You can also upload photos to go with tips or the location itself _ such as to show a cool vintage sign on a building's facade. Those will be available for anyone using Foursquare to see.

Only your friends on Foursquare and friends of your friends will be able to view comments.

Foursquare is one of a growing number of startups that let users broadcast their location to friends and strangers using a phone application. By far the biggest among them is Facebook, which recently introduced Places.

Foursquare has more than 5 million users, and they check in with the site more than 1.5 million times each day. Users earn virtual badges once they've earned a certain number of check-in points or complete a task, such as riding a ferry. Users can become ``mayors'' by checking in at a location more than any other visitor.