With the hype surrounding the new Nokia Windows phones, perhaps we will start to see more apps developed for the Windows Phone 7 marketplace. To get any traction, new and existing apps are going to need some healthy promotion to reach customers. The Lithuanian cross-promotion network, AdDuplex, seeks to help developers gain traction and monetize their apps through in-app advertisements.

To take part in this cross-promotion network, you need to add AdDuplex’s AdControl to your Silverlight or XNA Windows Phone application so they could start serving ads for other WP7 apps. In return, other apps serve adds for your application. It’s free to take part in the cross-promotion, but to support the service, AdDuplex puts in their own advertisements two out of every ten times your add would be shown.

The text-based advertisements have provided some success stores. In a recent blog post, AdDuplex presented a case study of AppFlow’s daily downloads which doubled with their cross-promotion campaign. You can see when Appflow joined AdDuplex– right before the spike in the middle. Of course your app’s mileage may vary. There are many external factors like the strength of your keywords that determine a good advertising campaign.

Say you’ve already got traction and are just looking to make money off of your WP7 app, AdDuplex is also happy to serve adds for you, however, they claim that’s not their main focus.

Many have heard of Finland’s Applifier, whose Facebook cross promotion network hit 55 million users in 4 months. There’s obviously a great deal of potential in these cross promotion programs if they can hit a critical mass. The WP7 userbase is much smaller than Facebook’s, but depending on the success of Nokia’s new handhelds, perhaps AdDuplex is positioned in the right place at the right time.