Hoping to build upon the power of its Internet leading search engine, Google is believed to be developing <A HREF="http://news.yahoo.com/s/ap/20050621/ap_on_hi_te/google_wallet">an online payment system</A> that would pose a stiff challenge to online auctioneer eBay's industry-dominating PayPal service. Industry analysts, merchants and investors were digesting reports Monday that the Mountain View-based company is testing a payment system--codenamed "Google Wallet"--in hopes of rolling out the service later this year.