I found several (textual) references to Android SDK API 8 in JDeveloper.
One was already mentioned by Joe (The one in the tools--> Preferences --> ADF Mobile and then the hint text for the example Android Platform Location)
There is also a reference in the Android Deployment profile where the default SDK is set to 8.
When you click to help on the deployment profile properties, it will also tell you that the minimum supported version is 8 which is not true IMHO (and according to Beta Refresh Participant Guide).
In the developerguide there are screenshots for both the Mobile Preferences and the deploymentprofile referencing API 8 as well.
And also page 3-2 of the devguide tells me that "Android SDK with Platform 2.2 or later" is supported.
Please also refer to the ADF Certification Matrix for details. http://www.oracle.com/technetwork/developer-tools/jdev/jdev11gr2-cert-405181.html. The ADF Mobile related certification info, including certified devices, OS, and mobile SDK versions, would be posted to this location when ADF mobile is released.