Share 'is there a way to alert someone that you see is online that you are on, so you can chat with them ?'

this is other than the doing the obvious thing of checking to see if they are chatting, and or posting a chat comment directed at them, there are allot of times i will get on here and know one will be in the chat room talking, but i will see people i know and like to chat with online, but like myself they may be surfing the site and not always look at the chat page, is there another way to alert…