Flurry admits that it is similar to Apple’s own Genius feature, which recommends applications to iPhone and iPod touch users. However, there are two main differences: The Genius feature is a separate tab that must be deliberately touched by the user to open it, whereas Flurry can recommend apps within apps they already use. Likewise, Genius is based on apps people download, but don’t necessarily use.

Flurry says more than 450 companies are already using AppCircle on the iPhone and a version will come out for Android in August. The service gets a little complicated with publishers earning 60 percent of the price promoters pay for each app download (which fluctuates based on a bidding system, but is currently somewhere between $1.25 and $1.50). Developers who use both aspects of the service receive a credit that is reinvested into promoting their applications. Currently, Flurry’s analytics are used within 45,000, so the service would only make recommendations off of the apps Flurry knows about on a user’s phone.

Even beyond Apple’s own Genius service, there are other companies trying to solve this problem. AdMob has the “iPhone Download Exchange,” which allows application developers in its ad network to allocate a portion of their ad inventory to an exchange to help each other drive downloads. Likewise, Mobui, a mobile app agency, which is a referral network.