Researching Bluetooth modules, it’s evident how darn expensive they are. $30 and up, usually. This is for small quantities but the regular stores don’t give a reasonable price even for larger quantities. I did find the aptly named Wireless Bluetooth RS232 TTL Transciever Module at DealExtreme for $6.60 (free shipping, of course). I haven’t got around to evaluate it yet.
But I also noticed these mini Bluetooth USB adapters for ridiculously low prices. DealExtreme has one for $1.80. I got two from eBay for $3.50 plus shipping. How can a retail product sell for so low compared to the main component inside??
Anyway. The dongle was easy to pry apart. It contains a bunch of 0402 passives, a BT chip, probably a USB interface chip and a SOT23 voltage regulator. On the top side, a single LED and through-hole 16MHz(?) crystal. Then I realized I wasn’t the first to take one apart: http://www.sparkfun.com/news/282
Then again, the dongle I got uses an entirely different circuit…