The iPhone continues to dominate the landscape for mobile applications, according to a report on mobile phone usage in April by analytics firm Flurry.

The data shows the iPhone dominates the landscape for mobile apps usage at 56 percent. It is followed by the iPod Touch at 28 percent and Google Android at 16 percent.

That represents a slight slip for Apple and a gain for Android. In March, the iPhone and iPod Touch accounted for 87 percent of usage, compared to the combined 84 percent in April. In March, Android only had 7 percent of usage.

Flurry measures the use of 100 apps across four platforms used by 14 million consumers. Games are a commonly used app on both the iPhone and iPod Touch. The latter represents a threat to the Nintendo DSi, since the demographics for the iPod Touch are teens or younger, closely mirroring Nintendo’s demographics.

Flurry says that 18 percent of users will upgrade an iPhone app they have downloaded within two months. When using their applications, consumers are most likely to do so using Wi‐Fi networks (see right). This is not just for iPhone games, but for all types of applications, according to Flurry. The use of Wi-Fi represents a threat to carriers who face competition with Wi-Fi. Likewise, users of the iPhone’s Skype application can circumvent carrier fees by making free calls over the Internet.

The lifespan of an iPhone game (top chart) hovers around three months. Peak consumer usage is around 6 – 8 weeks. After that, users tend to replace the app with something else they download. A few classic card games with social components are the exception, but most apps stick to this trend.

Apple announced last week that more than 1 billion apps have been downloaded from the AppStore. According to Mobclix, there are more than 41,049 apps in the AppStore now, including 9,115 free apps. Of the grand total, 9,002 are games. There are now more than 37 million iPhones and iPod Touches in the market.

Flurry has more than 5,000 developers using its mobile analytics tools.