According to
https://developers.facebook.com/docs/tutorials/mobile-app-ads/ , to notify Facebook of installs of your app, you can do the following:
For Android 3.0, add the following to onResume() of each Activity in your app:
com.facebook.Settings.publishInstallAsync(context, YOUR_APP_ID);
If we want to support Android devices < 3.0, is there another option? Or will this work in older Android versions despite what the docs say?
The docs are unclear–this will work on most pre-3.0 Android devices.
The “3.0” mentioned there refers to the version number of the Facebook SDK for Android rather than to the version of the Android OS.
All that said, the Facebook SDK 3.0 for Android and recent (as of Jan 2013) versions of the Facebook app do require Android 2.2 Froyo.