Twitter today announced plans to add "points of interest" to all tweets, via a "Places" API.

During his keynote address at the Twitter developer conference today, Twitter CEO Evan Williams said that if you were at a museum, you could tweet from the museum and attach your location.

Then you, or anyone else, could click on a map and see all the tweets coming from that spot.

It sounds a lot like Twitter is building the same functionality as startups Foursquare, Gowalla and even Hot Potato. You're basically checking in, telling the world where you are and what's going on.

On stage, Evan tried to preempt this talk, saying, "We're not trying to duplicate Foursqare and Gowalla," adding, "What we care about is what is happening in that place. Not just where you are."

Reached by email, both Dennis Crowley of Foursquare and Josh Williams of Gowalla told us they don't see Twitter Places as a threat.

Dennis said, "I've always thought we were complementary. We've been talking with these guys and working with them on ways we can both make better use of the overlap of the focus on location. Tweeting from a place is different than a checkin. Lots of products use location to encourage conversation and Twitter entering the space just makes those conversations more interesting."

Josh agreed, saying, "Gowalla already allows you to push your location to Twitter, and we're looking to deepen our integration to make sharing place related tags with Twitter even easier. In fact, I believe a significant portion of place-related tags attached to tweets will ultimately be generated from Gowalla. We believe there are times that you're going to want to share where you are in a broad sense through a service like Twitter — and we want to provide the best product to do that with. Other times, you're going to want to share with a select group of people — and we want that experience to be remarkable in Gowalla as well."

See Also: I’ve Used Foursquare for Three Months And I Am Addicted