Incentivized phone calls are becoming yet another way mobile app developers can bring in revenue.

Tapjoy is partnering with Santa Barbara-based RingRevenue to put phone calls to advertisers on its offer walls. If a user clicks through and calls an advertiser, they can earn virtual currency in a game or access paid content without paying for it. The advertiser pays based on whether a consumer takes an action like making a purchase, getting a quote or finishing a phone survey. Tapjoy says it’s already supporting 1,000 incentivized calls a day through its beta with partners like Allstate insurance.

For developers on Facebook, iOS and Android, offers have long been a key way of earning revenue without asking users to buy an app or virtual currency. Because most apps usually see 2 to 6 percent of their users pay, offers have become an important way to monetize the remaining 95 percent or so.

But offers lost a little bit of their power last year when Apple cracked down on giving users rewards for downloading apps. Since then, the advertising and offer networks have tried alternatives like letting users watch video ads for virtual currency in their favorite game or migrating to Android, where incentivized app downloads are still allowed.

Compared to app downloads or watching ads, phone calls probably have a lower conversion rate since it’s hard to predict how long a phone interaction will take. Watching a 30-second ad is an easily quantifiable time investment, so it might make users less hesitant to agree to seeing them.