Custom catalog price rule condition

Question

I have both android and web application running. Now i'm trying to assign coupon that can be redeemable only in mobile application.

To achieve this I've done below steps

Step 1 : To differentiate the order, I've created a custom column named order_via in sales_flat_quote table.

Step 2 : Using event observer i'm modifying order_via. i.e, when a product is added to cart via mobile it's order_via value is Mobile App and Web when it is placed via web application.

Step 3 : Extended Mage_SalesRule_Model_Rule_Condition_Address to add custom Cart Attribute i.e, Order Via to existing rules (screenshot) using below code

class Namespace_Module_Model_Rule_Condition_Address extends Mage_SalesRule_Model_Rule_Condition_Address {

    public function loadAttributeOptions() {
        $attributes = array(
            'base_subtotal' => Mage::helper('salesrule')->__('Subtotal'),
            'total_qty' => Mage::helper('salesrule')->__('Total Items Quantity'),
            'weight' => Mage::helper('salesrule')->__('Total Weight'),
            'payment_method' => Mage::helper('salesrule')->__('Payment Method'),
            'shipping_method' => Mage::helper('salesrule')->__('Shipping Method'),
            'postcode' => Mage::helper('salesrule')->__('Shipping Postcode'),
            'region' => Mage::helper('salesrule')->__('Shipping Region'),
            'region_id' => Mage::helper('salesrule')->__('Shipping State/Province'),
            'country_id' => Mage::helper('salesrule')->__('Shipping Country'),
            'order_via' => Mage::helper('salesrule')->__('Order Via')
        );
        $this->setAttributeOption($attributes);

        return $this;
    }

}

I created a coupon with my new condition i.e Order Via Web. I've applied it in cart page but it's not working.

I think i need to add this custom column_id i.e, order_via to existing object. Don't know how. Any solution to make this work.