I bought some rayson BTM182 bluetooth modules. They are pretty low cost and easy to find on the internet.. BTM182 has built in PCB antenna and part of large family, which are all very similar. There are without without antenna, class 1 etc...
Main problem with that modules is documentation. There are some AT commands described in the datasheet, but many of commands remain undocumented. I made some blind AT command testing without proper success. Then I dig into web search for more documentation and found out the UK company http://www.lm-technologies.com
use rayson modules. What is the most interesting is they have complete AT commands specification. I think this could be helpful for someone using that modules.