Bluetooth SPP (Serial Port Protocol) and Cobra Tag
Check the Cobra Tags FAQ
 Answer to first and second question.

Can I use a Cobra or other manufacturer’s Bluetooth headset for
handsfree talking while using this product?
Yes you can. The Cobra Tag uses a different Bluetooth communication
link than the headsets (called serial port profile) so they can both
work together.



How many Cobra Tags can be connected to one mobile phone?
The maximum number with some phones is 7. The maximum number that can
be paired with iOS devices is 1. This is based on a technology
limitation. It seems that some phones can’t simultaneously handle 7
Tags and are better off with 1-5 maximum.


 Answer to Third question.
SPP emulates a serial cable to provide a simple substitute for existing RS-232. Architecture of cobra tag shows it doesn't need complex data manipulation and just requires a few set of commands for its operation. I'll suggest sticking to this profile only.