Have you ever wanted to know who else is at your friend’s birthday party without having to send ten text messages  to confirm your ex isn’t there? According to InsideFacebook.com, Facebook now offers a checkin feature for Events, available for users of the Facebook mobile Touch site. Soon, the service will be expanded to the iPhone app as well. Once a Facebook user is in geographical proximity to a public Event on Facebook occurring on the same day, they can check in to the event on Facebook using touch.facebook.com. The user does not have to be invited or RSVP’d to the Facebook Event, but once checked in, the Facebook user will be added to the attending list and noted on Event wall as “here” at the event. Soon, iPhone users will have the option to check in to Events on Facebook as well.

This feature to check in to Facebook is already available for Facebook Places, which offers privacy options such as the ability to prevent your checkins from being publicly shared on Facebook place or on your own wall. (It can also prevent your friends from checking you into places for you.) These options are especially helpful when you want to reap the benefits of a checkin to a Place (such as a discount) but don’t want all your friends to know where you’re at. There has been no announcement yet regarding similar privacy options when checking into Facebook Events.

Facebook Places also offers business owners analytics to track checkin data and related user demographics. Similar tracking data is not yet available for Event owners, but would be undoubtedly helpful, especially for larger events. For now, there is limited data available in terms of attendance numbers. On the mobile interface, checked in friends appear as stories on the info tab marked as “here.” On Facebook.com, those who are checked in to the Event appear in a new “[#] Friends Were Here” section. This data could help party planners track not only total attendance, but peak traffic times at the event itself.