Is it any different than going through all your friends' pages one-by-one?
If it matched it with outside data (like Foursquare to see how often or when single friends go to bars or even identify which ones at which times), that would definitely be creepy.
The problem with the similar "Girls Around Me" app from a few months ago was it used all public Facebook and Foursquare profiles. As far as I can tell, this is limited to your own friends.