Magento 1.9 – How to Get Correct Store Context in Product Save Observer

You can do this job via standard event/observers:

<global>
     <events>
        <catalog_product_save_before>
            <observers>
                <some_module_detect_product_changes>
                    <type>singleton</type>
                    <class>some_module/observer</class>
                    <method>detectProductChanges</method>
                </some_module_detect_product_changes>
            </observers>
        </catalog_product_save_before>
        <catalog_product_attribute_update_before>
            <observers>
                <some_module_detect_product_attribute_changes>
                    <type>singleton</type>
                    <class>some_module/observer</class>
                    <method>detectProductAttributeChanges</method>
                </some_module_detect_product_attribute_changes>
            </observers>
        </catalog_product_attribute_update_before>
</global>

And Observer.php:

class Some_Module_Model_Observer{
    public function detectProductAttributeChanges($observer)
    {
        $attributesData = $observer->getEvent()->getAttributesData();
        $productIds     = $observer->getEvent()->getProductIds();

        $user  = Mage::getSingleton('admin/session')->getUser();
        foreach ($productIds as $id) {
            $change             = Mage::getModel('some_module/changes');
            $change->product_id = $id;
            $change->new_values = print_r($attributesData, true);
            $change->user_id    = ($user) ? $user->getId() : NULL;
            $change->created    = now();
            $change->save();
        }
        return $this;
    }

    public function detectProductChanges($observer)
    {
        /**
         * @var $product Mage_Catalog_Model_Product
         * @var $user    Mage_Admin_Model_User
         */
        $product = $observer->getEvent()->getProduct();
        if ($product->hasDataChanges()) {

            try {
                $user       = Mage::getSingleton('admin/session')->getUser();
                $attributes = $this->getAttributes();
                $new        = array();
                $org        = array();
                $changes    = array();
                foreach ($attributes as $attribute) {
                    if (!is_array($product->getData($attribute))) {
                        $new[$attribute] = ($product->getData($attribute)) ? $product->getData($attribute) : null;
                        if (!is_array($product->getOrigData($attribute))) {
                            $org[$attribute] = ($product->getOrigData($attribute)) ? $product->getOrigData($attribute) : null;
                            if (($new[$attribute] != $org[$attribute])) {
                                $changes[$attribute] = array('new'=> $new[$attribute],
                                                             'old'=> $org[$attribute]);
                            }
                        }
                    }
                }

                $stokAttributes = array(
                    'qty',
                    'manage_stock',
                    'is_in_stock',
                    'min_qty',
                    'min_sale_qty',
                    'max_sale_qty',
                );
                if ($product->getStockItem()) {
                    foreach ($stokAttributes as $attribute=> $value) {
                        $new[$attribute] = ($product->getStockItem()->getData($attribute)) ? $product->getStockItem()->getData($attribute) : null;
                        $org[$attribute] = ($product->getStockItem()->getOrigData($attribute)) ? $product->getStockItem()->getOrigData($attribute) : null;
                        if ($new[$attribute] != $org[$attribute]) {
                            $changes[$attribute] = array('new'=> $new[$attribute],
                                                         'old'=> $org[$attribute]);
                        }
                    }
                }


                $newValues = array_intersect_key($new, $changes);
                if (count($newValues)) {
                    $oldValues = array_intersect_key($org, $changes);

                    $change             = Mage::getModel('some_module/changes');
                    $change->product_id = $product->entity_id;
                    $change->sku        = $product->sku;
                    $change->name       = $product->name;
                    $change->new_values = print_r($newValues, true);
                    $change->old_values = print_r($oldValues, true);
                    $change->user_id    = ($user) ? $user->getId() : NULL;
                    $change->created    = now();
                    $change->save();
                }
            } catch (Exception $e) {
                Mage::log($e->getTraceAsString(), null, 'product_changes_fault.log');
            }
        }
        return $this;
    }

}

Here is I used Changes model to save every changes to DB. And you may create admin grid to view tracked changes on dashboard.

I'm not sure if this is what you need, but here is a simple extension that allows you to get the product url.
The main idea is to rewrite the info method in the product api model and make it return the url of the product also.
For this you will need the following files:
app/etc/modules/[Namespace]_[Module].xml - the declaration file

<?xml version="1.0"?>
<config>
    <modules>
        <[Namespace]_[Module]>
            <active>true</active>
            <codePool>local</codePool>
            <depends>
                <Mage_Catalog />
                <Mage_Api />
            </depends>
        </[Namespace]_[Module]>
    </modules>
</config>

app/code/local/[Namespace]/[Module]/etc/config.xml - the configuration file

<?xml version="1.0"?>
<config>
    <modules>
        <[Namespace]_[Module]>
            <version>0.0.1</version>
        </[Namespace]_[Module]>
    </modules>
    <global>
        <models>
            <catalog>
                <rewrite>
                    <product_api>[Namespace]_[Module]_Model_Product_Api</product_api>
                </rewrite>
            </catalog>
        </models>
    </global>
</config>

app/code/local/[Namespace]/[Module]/Model/Product/Api.php - your new class

<?php
class [Namespace]_[Module]_Model_Product_Api extends Mage_Catalog_Model_Product_Api {
    public function info($productId, $store = null, $attributes = null, $identifierType = null){
        $product = $this->_getProduct($productId, $store, $identifierType);
        $result = parent::info($productId, $store = null, $attributes = null, $identifierType = null);
        //add a new element in here called product_url. You can even wrap it in some condition to see if the product is assigned to the current website or if the product is enabled or visible. ($product->getWebsiteIds(), $product->getStatus(), $product->getVisibility()). 
        $result['product_url'] = $product->getUrlInStore($store);
        return $result;
    }
}

Note: This works only for API V1. In order to make it work for v2 you need to add a wsdl to your module. See how you can do it.