On Tuesday Yahoo introduced two new search iPhone applications at the C.T.I.A. conference in Las Vegas.

One of the apps, called Yahoo Search iPhone App, is an integrated search service for the Apple iPhone and includes a number of interesting features, including voice search and “Shake to Clear,” which does exactly what the name describes: clears the last search when you shake the phone.

The new app also offers a range of new local tools and features  that can refine a Yahoo search based on a user’s current location and also add relevant maps using location-aware technology.

The other new iPhone application is called Yahoo Sketch-a-Search.

The service works by allowing users to draw a boundary on a map around a specific location. The app will then bring up local content, including restaurants and businesses, without a user needing to know the name of an area or neighborhood. In addition, the app also filters restaurant results by cuisine, ambiance and star rating, Yahoo said.

The release of these new applications and other recent mobile content shows Yahoo’s continued efforts to stay involved in the growing mobile space.

In the early days of the Internet on cellphones, Yahoo was considered a thought leader, releasing numerous mobile applications around news, search, mail, and chat. Over the last several years, Yahoo’s competitors have quickly surpassed the company by releasing handsets, operating systems and entire ecosystems around devices.

The Yahoo-Twitter partnership would be comprehensive and more encompassing than Twitter’s search partnerships with Google and Bing, but now Yahoo tells us that the integration will focus on three primary areas:

- Access to your Twitter feed on Yahoo: On Yahoo Mail, Sports, the homepage, and other Yahoo properties, you will be able to check the most recent tweets of your friends.

- Ability to update status from Yahoo: Yahoo will become a Twitter client, allowing you to update your status from multiple locations on Yahoo. We’re not sure if this is going to be through widgets or another method.

- Yahoo Search and media integration: Public Twitter updates will be integrated throughout Yahoo Search, News, Finance, and Entertainment, among other properties.

Yahoo will have full access to the Twitter data firehose, so you can expect real-time updates in Yahoo Search, among other integrations. They will use tweets to improve relevancy, freshness, and search results, as well as “drive deeper user engagement.”

The first integration will be available “immediately,” and that is the real-time search integration. This brings Yahoo Search in line with its competitors in terms of real-time data. You can probably expect this to launch fully later tonight or early tomorrow.

As for the other integrations, they will launch later this year.