Bluetooth Trancievers for arduinos
The boards in your link look funny.  Typical boards like this include the "bluetooth circuit" which piggy-backs onto that board, and is soldered at all those little pads.

Have a look at say, the HC-05 board ~  https://www.google.com.au/search?q=hc05+bluetooth+module&amp;tbm=isch

It's easy to see the part that's missing from the one in your link.

For these HC-05 boards, it's possible to pair two together.  They need to be configured as "Master" and "Slave" though.  Some bluetooth boards can do slave-mode only, so be careful before you purchase.