Since you already have the one, and the other is on its way, there's
one way to find out (sort of). I suppose this would involve making
three rides as identical in all parameters as possible - one with the
one unit, one with the other unit, and one with both units, then
comparing results. I guess if anomolies were suspected using the
combination you'd then want to do more sets of 3 tests - maybe
changing conditions to illuminate and zero in on revealed anomolies.
Or (I'm assuming these gadgets must have some kind of wireless data
transmission you're concerned about) you could look up the technical
specs and see if the devices "say" anything that the other could
"hear".
Asking on usenet is not a bad idea, either - as long as you don't mind
smartass remarks from people who don't know the answer but are
compelled to compensate ;-)
I have a pair of dolls - Bart and Homer Simpson - that converse with
each other. You just need to place them in proximity and activate one
- it's really great.
(Might want to re-line your helmet and shorts with tin-foil shielding
just in case, though.)