You can put the hack anywhere you like. most of the template change is to have it float but will I was working on the code, it did actually start in the navbar
Ill give people a couple of options, floating or in the navbar, you can pick in the options for it. Poet - Ill do that but it looks a bit strange "You have no new PMs" and then a flashing envelope
I did find a bug this morning though, after posting this of course

If youre a guest, it still asks the server for your PM count. As youre a guest, you get permission denied that causes two things. Firstly, IE borks on it if you have Microsoft Script Debugger installed (go figure, IE sucks) and it ups your bandwidth bill.
Ill upload v1.1 tonight that will fix all that.
If you dont want it to hit the server but still want the flashing floating icon, set the timer to 5 million or something insane. It still checks everytime the page is loaded.