Yup, simple, just create a new script in Plus > Preferences > Scripts and copy this over everything in the script:
code:
function OnEvent_SigninReady(sEmail){
    var contacts = Messenger.MyContacts;
    var online = 0;
    var total = 0;
    for(var e = new Enumerator(contacts); !e.atEnd(); e.moveNext()){
        item = e.item();
        total++;
        if(item.Status != 1 && item.Status != 0){
            online++;
        }
    }
    MsgPlus.DisplayToast('Online',online+'/'+total);
}
I'll make a script pack if you want, but doesn't really seem needed.