Voice search for mobile phones is one of the killer applications  – just think of all the people for whom mobile is the main tool for connectivity and they do not prefer to – or simply cannot – type. How nice it would be if the phone understood your speech and provided accurate information based on your voice commands? Well we are not there yet … but there are some positive developments. When Google and Microsoft step in, things move fast and people pay attention. Here’s a summary based on a recent WSJ article.

Google released a free experimental service last week called Google Voice Local Search. It allows users to dial a number 1-800-GOOG-411 (in US) and search for businesses in specific cities, using technology that recognizes what callers speak. It will connect you to the business or you can get the results via SMS.

Google’s test announcement comes a few weeks after Microsoft announced plans to buy Tellme Networks  for a price that people familiar with the matter put at $800 million. The closely held Silicon Valley company specializes in services that combine voice-recognition technology with the Web, and already provides automated directory-assistance services for AT&T Inc. and Verizon Wireless, a joint venture of Verizon Communications Inc. and Vodafone Group PLC.

Yahoo is also planning to enter the voice search race, which is largely driven by the huge opportunity to sell ads that will run on mobile phones— and by the fact that Google doesn’t dominate that business, as it does for searches that use computers. Yahoo officials say spoken queries could eventually become an option; two executives from Tellme recently joined Yahoo.

The Journal Adds:

Until recently, voice recognition has mainly been used by telephone carriers and companies to lower their costs by reducing the need for live operators. Recently, that technology also has been used by some new entrants to provide free, ad-supported alternatives to paid directory assistance, such as Jingle Networks Inc.’s 1-800-FREE411 service.

The latest push by technology companies is also designed to make voice-based searches better, not just less expensive.

Google’s experimental service, like the Web, can work even if callers don’t know the name of a business they want. A user can ask about a type of business, such as a coffee shop, and specify an intersection or ZIP Code. The service will read off a list of nearby businesses that fit the criteria.

Another step, being pushed by Tellme in a service it has been testing, is to let users start with a spoken query, but display the results from that question on the display screen of their handset. Besides the name of a pizza shop, for example, a user could instantly see a map to it. That capability, which requires software downloaded to a handset, could also ultimately help the user complete a transaction, such as order a pizza.

“Voice is a great way to input information,” said Angus Davis, a Tellme co-founder. “It’s not always the best way to get output.”

Combining other kinds of information also can improve searches. Verizon, using technology from start-up Medio Systems , allows users to speak the name of ringtones, games or other things they want to buy. The technology can guess whether callers are interested in, say, the weather in Seattle or a band called Weather in Seattle by analyzing their past searches, said Brian Lent, Medio founder and chief executive.

Microsoft, besides mobile search, says it plans to use Tellme technology to add voice input for many products, including computers and hand-held devices. A spokeswoman for Google said, “having quick, free access to local business information over the phone may prove to be very valuable to our end users.”