Startup Idea : See who's with you at a place

I was thinking, at an event you have lots of people. What if there is an APP in which you have your own profile and everytime you are at an event your check in and see a list of all the other people with profiles who are also checked-in. Think like this: your are so drunk or busy and you see someone interesting, you can connect with this APP instead of giving your mobile phone number. This is for public events or private meetings.