While the smartphone market grows at surprising speed, the contrary dynamic for content developers is it's becoming harder to generate revenue from each new user, compared to early adopters.

It's particularly the case because of the proportion of free games now available, something forcing developers to think about new ways of monetisation, either through gameplay focused around in-app purchases, or advertising.

Hence, Apple's decision to ban the most effective advertising solution - the incentivised download or offer wall model, implemented by the likes of Tapjoy and Flurry - hasn't helped the situation any.

It's a Kiiper

Still, it was good news for Kiip (pronounced Keep). The year-old US alternative ad network, founded by Brian Wong, has already raised over $4 million VC funding.

"Tapjoy was very effective, it's just Apple threw a hissy fit and it took the brunt, but we've got a lot of inbound from developers who ripped it out and needed an alternative," Wong says, cheerfully.

In contrast, Kiip is an achievement-oriented advertising network, in which rewards - currently real world offers but in future virtual coupons and currency - are integrated into the achievement systems most mobile games now operate.

"Achievements are universal but it struck me no one was making use of them in a marketing context," Wong says.

"It makes complete sense to use them as at that point the player has an heightened emotional state and it's a natural break in play."

The first wave

Currently live only in the US in a controlled beta for iOS and Android, Wong says "more than 10 million users" can be accessed through the dozen or so games and a couple of apps that support the network. Ad clients include the likes of Dr Pepper, Carl's Jr and Sephora.

He won't reveal the titles running Kiip though, as the company is worried people will game the system, downloading them just to get the rewards and then stop playing, increasing churn.

"We want people to stumble upon the rewards, rather than feel entitled to them," he explains.

Wong claims early feedback is excellent however, for users, developers and advertisers. "We're seeing redemption rates in the double digits across the board," he says.

"It's sad benchmarks of 0.1 percent in terms of click thru rates have been considered excellent in this industry, but that's obvious if you consider the quality of banner advertising."

Pumping the makers

It's developers that Wong's really excited for, though.

"Using Kiip, developers get paid on inventory they've never earned money from before, and they're giving their users free stuff," he says.

Also, because Kiip isn't a traditional ad network, there's no reason developers can't use traditional banner networks as well, although Wong doesn't think it creates the best user experience.

"It's not an either or thing," he says. "They can continue to use AdMob or Millennial if they really want to."

Still, the advantages of Kiip are the more subtle attractions it can enable.

"When we talk to developers, we found many of them had been using Tapjoy to improve their user retention, because offer walls are the only way to keep players who don't want to spend money engaged in your game," he explains.

And that's why extending Kiip to enable advertisers to sponsor virtual currency is next on the to-do list, alongside rolling it out to more developers, advertising clients and countries.

"We're all about rewards, revenue and retention," Wong says. "That's why we're a no-brainer."