RocketConBungee allows you to use rCon directly from BungeeCord's console.
The command is:
/rcon hostort password command
/rcon localhost:25566 mysuperpass say Hello World
Why is it useful? You can set people's rank when they purchase it from Bungee on (put your amount here) servers. You could do this from your PHP script if you have your own ItemShop, but if you use one at some hosting it may allow you only to execute commands on one server, which would be your BungeeCord