BrandMeister maintains a Last Heard list. This is a real-time list of all activity on the network.
You can find the list heard page at https://brandmeister.network/?page=lh
The last heard page shows all activity worldwide. You can open the search panel and create a filter to restrict your view to a single master, repeater, talkgroup, call sign, radio ID, and a few other things.
On each row, you may notice a speaker icon in the Destination column. This is a link to the Hose allowing you to listen to the conversation.
Reference
BrandMeister Dashboard: http://brandmeister.network
BrandMeister Last Heard:https://brandmeister.network/?page=lh
BrandMeister Hose: http://hose.brandmeister.network
BrandMeister Getting Started Guide: http://papasys.com/dmr/BrandMeisterGettingStartedGuide.pdf
User Guide: http://dmrx.net/files/US_BM_User_Guide.pdf