three independent android applications
If I am interpreting your wording correctly, and you mean that you want 3 APKs that are usually all on their own together in one APK, then this is not possible. This means that a modular Android application (a common appliance of such functionality) is also not possible.
On the other hand it is possible to have multiple Activities show up in the launcher by adding this intent-filter in the AndroidManifest.xml to the Activities you want to have visible:
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>