cargoWorldDefense provides a LibDataBroker object which displays the current attacks on your homecities by parsing the WorldDefense-Channel. The tooltip displays the number of last attacks on different areas within 5 minutes and the time since the last message was received.
I made this mostly because of the Zombie Invasion as I wanted to get an overview which cities are under attack, but didn't to see the WorldDefense-channel spamming.
As it does not provide its own display, you'll need a LDB-based display addon. (So, your display can differ from the screenshots)