Any suggestion on how to do and what kind of boards to use?
Any generic Bluetooth module should work. Just do a search for bluetooth module.
But most of them use 3.3V Levels, so you may have to add some level shifters in between.
(most esiest ist to use some standard CMOS buffer ICs or even some simple transistors)
But that depends on the specific module and I can not answer this in general - all are different. Some have level shifters integrated, some not.
Some have RS232 Shifters with +-12V so you have to consult the modules documentation.