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Arduino Pulse Sensor (Best Type of Arduino to Use?)

I am making a pulse sensor using an arduino, and I was wondering what type of arduino would be the best for this project. Here is a link to the tutorial I am basing my design off of:

https://docs.google.com/a/hightechhigh.org/document/d/1FVFffuKD9OnkTOwxs3dVaxp5LYb4S1aj65MS6lvIZbA/edit?hl=en_US

My goal is to make the pulse sensor as compact as possible while still able to be powered by an external power source (so it does not need to be connected to a computer to function), and as of now I have access to a traditional arduino and a lilypad arduino...which could be used to make the pulse sensor compact, while still allowing it to be powered through an external power source? Thank you!