how to do diag in a free way

Few days ago, I didn’t know cellphone can do the diag on car until I heard that from someone in forum, then I keep asking how is that going, and today I think I may be totally know how it works, and What surprises me most is that the android app torque is free, which I used to be told the price is $25.
Now if you don’t mind, let me show you how it work with the adapter elm327(I am new, please don’t judge me):

There’s an app in the Google Play store called Torque. There’s a free and a paid version. Install the app on you android or symbian, and then connect to the elm327 bluetooth OBDII reader(3 .pdf may help) and read fault codes, clear them, and show RPM and other stuff. It’s pretty cool and it works.
Anyway, I really like to do this stuff on my phone, convenient
http://www.xcardiag.com/upload/pro/elm327-bluetooth-software-code-scanner-4.gif
http://pocketables.typepad.com/.a/6a00d83451c9ec69e20147e0db9dac970b-800wi