Wikipedia
Tagtile
Tagtile is a unique loyalty and direct marketing solution designed to grow one's business. It also acts as a customer management solution designed for local businesses. It was started by two IIT graduates, Abheek Anand and Shoham Mazumdar.
How it works: There is a customised tagtile cube that the business place connects to a power supply and the customers who have the tagtile app downloaded and installed in their phone will just have to tap on the tagtile cube once. That customer is then tagged and it becomes easy for the business person to keep in touch with his customers using Facebook and Twitter.
As of 25 April 2012, Tagtile was acquired by Facebook.