if by speakers you mean the sonar traducers on the VPS module that would not be a good place being it would block the sonar and possible make it think its always real close to the ground no matter how high up you were flying.
That's not entirely true and the trackimo does also send out a signal through its cellular connection to send the data to their server to be able to get the tracking info every time it pings its self.
Thought it doesn't interfere with any thing in the phantoms GPS or any thing else being its not the right frequency to effect any thing in the phantom. I also haven't noticed them even affecting the compass like a cell phone can if its powered on and to close to the compass. Though just to be on the safe side I keep my trackimo on the opposite leg then the one with the compass in it. Though unlike with my other phantoms I'm a lot less worried of it ever having a fly away on the p3 being that seems to be almost a none existent possibility with the new GPS and GLASNOS GSP that the P3 has and I have never even so much as had any thing that even causes me to even? The rock solid reliability of there GPS compared to all my others were any flight could be its last one before trying to make a run for it and take off..
So I mostly just use it on the p3 for the extra pcs of mind just in case it ever flew away.
Though the funny thing is that any time i ever had a fly away or even a near fly away on my fc40 or my p2v have been when I didn't have the trackimo on it. But I guess that's just how Murphy's law works any way.