This is a project I started to play with a bit, but haven't had time to finish it. There are two main parts you need if you want to create your own adapter that would cost less than $10. First, you need a max2322 rs232 to ttl converter. Second, you need an HC-06 Bluetooth adapter.

Here is a simple schematic with the pinouts (double check my work): https://drive.google.com/file/d/0B7W...ew?usp=sharing

This weekend is raining, hopefully, I will have some time to get back to this. If I have success with this, I will let you know.

PS, I have seen a similar design that uses a wifi module instead of the Bluetooth one.