This is an older thread - but since I am working on this stuff again I thought I would update.
As of API 17 (Android 4.2+), you can get a decent proxy for HDCP information from the standard Android SDK.
If you want to ensure that a display is "secure" you can call setSecure(true) on the application Surface. Then for good measure you can enumerate the available Displays and verify that FLAG_SECURE is set for each one. This will block DDMS and at least hint to the display driver that the output should have HDCP turned on. No guarantees though and your mileage may vary.
On further note -- the path Alex noted above may have changed on newer devices (Android 5.1+). But since this is dependent on the OEM, expect this may vary on different devices. :-(