The idea here is that instead of running the below script bamboo-agent.sh from a dedicated remote agent box and hence once per agent

./<Bamboo agent home directory>/bin/bamboo-agent.sh start
./<Bamboo agent home directory>/bin/bamboo-agent.sh stop
./<Bamboo agent home directory>/bin/bamboo-agent.sh status

allow to select one or more remote agents e.g. on the "Agent summary" page in Bamboo UI (Overview >> Agents) and open a menu for those with the options start / stop / status, so to perform these actions centralized.

For doing so, remote acces to the corresponding agent box can be setup and via that the script be called and its return be fetched (and displayed on the same page in Bamboo UI).

Consequently a started remote agent should move the agent to "online" and a stopped one to "offline" (online / offline already being present on this page).