If you know how far off any of those meters are from the TL and as long as it's consistant, you'd be fine. If the SPL Labs had a BT for the iPhone I'd be all over it. And I already own a TermLab.
I tested with the SPL Labs at the last show and it was pretty dead on when I got in the lane on the TL (I didn't have mine at the show). And it was just a mic streaming to the dude's phone. It was awesome.