Step 1: Preparation
A boarduino (or arduino)
A coodless phone
Acuple of wires
The first step:
since the Boarduino does not have a build in 5v regulator, I had to give it a voltage from 4.5v to 5.0v in order to not feed it 9v or anything higher.
I was looking at some stuff and I found a old phone with a 3.6v battery, I charged it and deceited to giver it a try. Turned out that it worked!!
NOTE: You need a cordless phone battery fully charged in order to make this work right and last longer....