Do a quick search, you'll get hits, but if you're thinking of going for a mobile connecting one and you have an iphone, you need wifi not bluetooth. Don't know if you're JDM or not but you need to check the reader if you are.
Couple of recentish examples.
http://www.350z-uk.com/topic/94389-what-bluetooth-obd-dongle-to-buy/
http://www.350z-uk.com/topic/101554-fault-code-reader/
There's loads on ebay/amazon but some of them just flat out don't work - at a few quid though, it's not a disaster.