"I owe you a beer" is a phrase that's thrown around a lot with very little follow through.
UMBC Alumnus Sean Kennedy (Information Systems '06) created a smartphone application that could change that. BeerGivr allows you to virtualy send your buddy a brew. When a friend wants to buy you a drink but can't make it to the bar, he can send a text message with a code that's currency in some local bars. As of now twenty bars participate in the BeerGivr project, among them Alewife, No Idea Tavern, and Bond Street Social.
You can read about the conception of Sean's app in a recent profile on InTheCaptial.com.