Conversation is an art. And, as with other art forms, creating a good conversation requires careful use of positive and negative space. In other words, you generally don't want one person dominating a conversation by talking all the time.
Technology to the rescue. The Talk-o-Meter is an iPhone app that's designed to give people feedback about how much they're talking in a conversation. You place your phone on the table and the app automatically recognizes the voices of the interlocutors and keeps track how much time each person spends talking. During the conversation, the screen displays the balance of talking time in 1-, 2-, or 5-minute intervals. If one person's talking much more than the other, you can see it on the screen. Right now the app only works for conversations between two people "who do not have similar voices and talk in a quiet environment." A version for conversations between more people is in the works.
It would be pretty passive-aggressive to pull this out when you sit down to coffee with a confessed chatterbox, but you could use it covertly if you're just curious about whether your conversations have an equitable give-and-take. We all like civilized discourse, right?