iPhone users can now rely on Google for a helping hand the next time they go shopping.

The search giant yesterday launched a version of its free Google Shopper app for the iPhone. The app, which has been available for Android users the past year, is essentially a mobile search engine for products, letting you compare prices and read reviews before you open your wallet.

The app offers several ways to search for products. You can type the name of the item in the search field. You can snap a photo of a book, CD, DVD, or video game or of a product's barcode. Or you can speak the name of the product.

In return, Google Shopper reveals a list of stores, both online and offline, that sell your chosen item along with their respective prices.

Tapping on a particular store drills down further where you can read product details, check out customer reviews, and bounce between a list of local retailers and online merchants who offer the item. Drilling down even further to certain retailers, such as Best Buy, the app can check on inventory at your local stores to tell you where you can find the item.

The app keeps a history list so you can always return to any past search. You can also mark your favorite products with a gold star, putting them into their own easily accessible category. Finally, you can share the details of any product you find with other people via Facebook, Twitter, or Google Reader, the company's online RSS feeder.

Google's description says the app requires iOS 4.0 and is compatible only with the iPhone and the fourth generation iPod Touch.

I tried Google Shopper with a variety of products, using text, voice, and photos, and the app performed nicely. It did have trouble at times picking up product barcodes through my iPod Touch 4G, but no problem zeroing in on the front cover of CDs, books, and similar items. Once it found the product, it typically showed me a lengthy list of retail outlets where I could buy it, even tapping into auctions from eBay.

Google Shopper is part of a growing list of similar mobile apps that deliver prices, names of retailers, and other details on a wide array of products.

Amazon released a Price Check app in November, which like Google Shopper, lets you find products by text, voice, or scanning the front of a product or its barcode. Another app called Scandit helps you track down products by scanning their barcodes. eBay also lets you search for products by scanning their barcodes, both through its own iPhone app and RedLaser, an app it acquired last year.