Finally i was able to blink a LED on my Arduino through an Android app. Well! it was a really glad moment for me. :-D



I have used a cheap Bluetooth module called RS232 BT Module even you could use this one as well.

 
Note that TX of BT module need to connect with Arduino's RX
And RX of BT module with Arduino's TX, I have wasted few hours to figure out this mistake :-D

BT-RX >> Ard-TX
BT-TX >> Ard-RX



Notes:
On bluetooth, Pair them-- default password is: 1234
My BT device name was recognized as : "Linode"

Tutorials I followed:
1. http://www.instructables.com/id/Cheap-2-Way-Bluetooth-Connection-Between-Arduino-a/
2. http://www.instructables.com/id/Androino-Talk-with-an-Arduino-from-your-Android-d/step2/Setup-the-Arduino-hardware/
3. http://english.cxem.net/arduino/arduino4.php