When I worked with nitinol I used an example straight from the book.
because you will need to control a large voltage (about 12 - 18v) to cause the nitinol to change, you probabbly want to check out page 96 in the arduino handbook that comes in the basic kit. I replaced the button in the diagram with a sensor made of velostat and put a series of sensors together in a similar orientation.
I used this exact set up with a 12v power supply because its stable... i've used 2 9v batteries, but they are notoriously unstable and over heat like crazy.
Good luck!