I need help with bluetooth

I am planning a small project with BT which must be connected with Android app. The problem is that everything must be as small as possible...what parts do you advise to buy??

I am planning a small project with BT which must be connected with Android app. what parts do you advise to buy??

Get serious. You must realize we need more information about your project than what you have provided. If you ask a direct question like what is the smallest arduino available the answer would be a Micro, Nano, or Pro-Mini. Some things can be done with an 8-pin ATtiny85 ic. (google it for datasheet) It has multiple programable I/O ( analog , PWM & digital.). Pro-Mini's can be found for $3

Thank you for your prompt response
I’d like it to fit in my hand.
I need to make a remote control.
This is my first project, so I was not quite that clear…All Advices are welcome

I just had good luck with the BlueSmirf from Sparkfun: https://www.sparkfun.com/products/12577

If you are 3.3 V, you can just get the RN-42 by itself.

You can use a Pro-Mini, Micro or Nano with that. They are all small.

I made a bluetooth control lamp which was controlled through my laptop.

This link was helpfull.

http://embeddedsystem1.blogspot.in/search/label/bluetooth

https://www.youtube.com/watch?v=3mzl83KJNJs

Again thank you all for your advice, It helps me a lot :) I'm very interesting in this ATtiny85.In what way can you program the chip. I saw on youtube that they use Arduino uno for that

http://highlowtech.org/?p=1695 (this is the MIT tutorial that almost everyone refers to about doing that..)

When I followed it I got a compiler error until I found a link where other people had the same problem and solved it by including a couple of *.h files. Here a link to the post explaining the problem and solution: http://forum.arduino.cc/index.php?topic=201063.0