notification pop up

Hi You have to make modifications to phpfox([login to view URL]) script package on my running live site. Current Status : If two users are online at same time on site and wants to communicate with each other (like chat 1-2-1) they are unable to do. Although there is chat system (1-2-1) is present there But user is unable to instantly send notification to other user (its should be a popup message-alert box) that i want to chat with you etc. Whenevr a user recieve message, comment, crush or any alert and if he is online then there is no way to let him know about this. Your Job: 1. You will enable popup-messgae-alert so that chat invitation can be sent instantly and it should popup on other user screen making it Top-of-All. 2. If a user recieves any message, comment, crush or any alert then also a top-of-all popup-message-alert should come up to let him know. Plz note it should be instant. Please quote your bid. My budget is very low.