You can use Tapjoy or GetJar.
GetJar is in the process of being upgraded (hopefully) - because they have a very slow server and hard to integrate SDK - plus their online portal is very old world. They are in a serious need of overhaul.
Meanwhile Tapjoy is fast/modern/efficient.
I liked GetJar and their payments (about $0.09 per app install - now seems to be $0.045 per app install i.e. 5 coins - developer gets 0.9 of that - so $0.045).
However, it was earning miniscule amount (compared to ads even - i.e. 1/10 or 1/20 of ad revenue).
Moved to Tapjoy and it is earning even less (!) So maybe one needs to do engineering to tune it … but anyway …
Tapjoy shows video ads also - but my impression is that inventory is low and video ads GENERALLY pay very low i.e. $0.01-$0.02 per view or something (this is just off the top of my head - what i feel it was …).
Basically the problem with Tapjoy/GetJar vs. IAP (Google Payments) is that you cannot tap into the “whales” as you can with IAP (cash payments/Google Payments). Since Tapjoy/GetJar require user to do considerable work to earn you $1.00 - and that kind of spoils it for “whales” - since the whole purpose of “whales” is that of using cash as “shortcut” in games (or perhaps in their lives - so maybe a very specific demographic).
So with Tapjoy/GetJar you wind up only being able to get trickle revenue - appropriate for the work the user puts in downloading and running apps (to earn the coins).
The second thing is this is “incentivized downloads” - and this pays LESS than non-incentivized (i.e. banner ads or AppWalls etc. where the user voluntarily clicks on an ad “they like” thus presumably that click or download is of more value than a non-interested user who just downloaded an app because it was paying more coins).
I’m seeing folks reporting here that Tapjoy/GetJar type stuff gets them 20% of their ad revenue maybe - there maybe some who are doing better because they have some really valuable feature - so in the right circumstances there MIGHT be a real value to Tapjoy/GetJar.
Note that the contradiction is that users who are NOT interested in your app (and click on an AppWall) - or users who just see an ad they like for an app - that revenue can be considerably more than what a user who is paying you for unlocking features can earn - so this is the thing for developers to ponder - they think that if they have a feature that users like they will pay for it - the reality is that they may wind up earning more just by having everything free and showing ads.
A wrinkle on this is to USE the concept of “earning” coins - in a secondary way - not really expecting users to earn Tapjoy/GetJar coins - but to have that as an option to “remove ads” - which can deflect some of the criticism about ads etc.
So you can use the concept of a Daily Reward to bring user attention to the fact that they can unlock features (without making it look like an ad/reminder - thus leaving space open to show an interstitial ad etc. - since Daily Reward will presumably generate some warm feeling in the user), and may presumably increase retention - if some users think that returning to app rewards them …
While the direct way of thinking is that just price the unlock features according to what you think you should earn - the reality is that so few will go that route, that one may then consider the value of offering a much easier path to unlocking - either by a low Tapjoy/GetJar coin number to unlock - or by making the unlocking ENTIRELY feasible to unlock just with Daily Rewards - there is the possibility that IF such a strategy can increase your user retention - it could raise your conventional ad revenue MORE than what you may make from your direct-thinking “why don’t they unlock features using Tapjoy/GetJar”.
So there are a number of ways of thinking about this. If you can just get users to return to your app 2x more often - that may double ad revenue (well …) - and that may be more earnings that any Tapjoy/GetJar stuff directly may do …
However, I suppose there could be situations where a feature is SO essential and so desired that one could get good conversion on the Tapjoy/GetJar as people jump to complete whatever number of coins are required to unlock that feature …