Rubbernet
Rubbernet keeps an eye on all network-enabled apps running on your Mac. It provides real-time monitoring so you can keep an eye on the exact state of your live network connections. With the Activity sidebar, you'll be able to see which applications are currently communicating over your network. When connections are idle, they will dim to let you know that traffic has stopped. Rubbernet provides a breakdown of per-app network usage, so you can quickly detect apps that phone home, connect to certain servers without your knowledge, or blame the app that's slowing down your network.
