BOSTON (Reuters) - The cost of talking on the go is coming down, thanks to an increasing number of options for using Internet calling services on mobile phones as an alternative to traditional cellular service plans.

Nokia is one of the biggest makers of mobile phones with Wi-Fi chips. Some high-profile devices are equipped with the short-range wireless technology, including Apple Inc's iPhone and some BlackBerry models from Research in Motion Ltd.

The soon-to-be-released G1 Google phone from HTC Corp and T-Mobile also sports a Wi-Fi chip.

For Mark Laris, a Dallas-based nuclear engineer who travels the world running his consulting business, the technology saves him thousands of dollars a year on international phone bills.

Wi-Fi chips and Voice over Internet Protocol, or VoIP, let him do most of his business and personal calls over cut-rate phone services that work over the Web. His only mobile phone bill is a 1,400-minute-per-month family plan from AT&T that he shares with a business partner.

"I always make VoIP calls," he says, adding that the call quality is as good as a traditional mobile phone service.

He accesses the VoIP services using a Nokia phone loaded with a Wi-Fi chip similar to ones that that allow laptops to access the Web in smaller venues like coffee shops.

The new phones are capable of operating just on Wi-Fi -- they don't necessarily have to use a mobile phone carrier at all -- and when you're not in a Wi-Fi "hot spot" they ring through to your Wi-Fi carrier's voice mail.

Still, mobile VoIP is a fledgling field.

In the United States, Deutsche Telekom AG's T-Mobile sells Wi-Fi phones and Internet calling plans for $10 per month on top of regular fees. It is the only U.S. carrier with such a package.

Otherwise the market is filled with small, privately held companies hoping to make a name for themselves. They include DeFi Mobile (http://www.defimobile.com), Fring (http://www.fring.com), Gizmo5 (http://www.gizmo5.com), Sipgate (http://www.sipgate.co.uk) and Truphone (http://www.truphone.com).