As of December 2012, the conversion key is the same for all new mobile apps created in the TMC Attribution Analytics solution. This consistency allows your engineers to implement the same SDK in all their apps. The Android package name / Apple bundle Id is then used to associate the SDK implementation with the mobile app created in TUNE.
Therefore, your engineers only need one key. If you have two apps with the same Android package name / Apple bundle Id, you can set the site_id (mobile app id) which overrides the lookup by Android package name / Apple bundle Id.
Now you don’t need to setup the mobile app in MAT for each new mobile app (that you implement the SDK into). If the SDK sends data to MAT, then before you create the mobile app in MAT, MAT automatically creates the mobile app using the Android package name / Apple bundle Id. When MAT creates a mobile app dynamically, you need to create a Campaign for the mobile app so you can generate tracking links and promote it.