You're trying to explore behavior that exists at a much lower level than the LabVIEW Bluetooth communication VIs. Communication functions in high-level programming languages tend to abstract away details like signal strength and packet structure, because 99% of the time, the programmer just needs to get bytes from point A to point B and isn't interested in the lower-level details. This is also the reason you don't see any degradation of the signal; with digital communications protocols, you tend to get either perfect transmission or no transmission (and an error of some kind).
Kileen had some ideas in
this thread a while back that you might want to check out. You'll probably have to resort to calls out to the operating system, or perhaps to the specific device driver of the hardware, to get signal strength information.
Regards,
John