I've bought a bunch of these modules:http://www.ebay.com/itm/Bluetooth-Transceiver-Master-Slave-Module-RS232-For-Arduino-2560-UNO-R3-A035-/251054166666?pt=LH_DefaultDomain_0&hash=item3a73fe928a
Mind there are tons of identical modules with different firmwares available.
The modules are connected to arduino via rx, tx, 3v3 and gnd pins - that's it. You may set them to different baudrates, names, passwords, as well as you can set ~50 various other parameters. They create a serial link, so your PC gets new COMs. You may connect several BT modules to your pc (or tablet) concurently (even with different baudrates, etc.). They shall work as a master/slave as well (not tested yet), so you may connect 2 or more arduinos together. The reach is about 10m. Power consumption see above.