The HC-05, a Bluetooth to serial bridge, can be found for around $5 on the internet and therefore may be the cheapest way to add Bluetooth connectivity to your project. However, its default setting… ...

The Arduino, Bluetooth module (check your specs, some HC-05, and HC-06 may come on a breakout board expecting 5V), and USB Host shield all run off of 3.3V, but devices you want to plug into the ...

The HC-05 is one of a series of castellated modules (HC-06, -07, etc). the JY-MCU is a breakout board for whatever version of module happens to be soldered onto it.

You know, we don't see too many didgeridoos in these parts (and for good reason, seeing as how it is little more than a pipe) but wait'll to you get a load of this aerophone-wielding maniac: Kyle ...