Controlling phone with arduino

I am working on a project that connects an accelerometer to an arduino. When the arduino/accelerometer pairing detects a certain amount of movement, I want my Android phone (or iPhone, I have both) to send a message to three contacts. How should I go about connecting the arduino with the phone in a way that the arduino would control the phone and not vice versa?

Hi,

You can try this one http://1sheeld.com/

Krishna

Anyone?

Why not use a GSM shield to send you a text?

Thanks for the response! We're designing this as a product and we don't think it would be reasonable to sell a sim card along with the product.

In that case you are probably looking at Bluetooth and then a phone will always have to be in range. Or wi-fi?