title: Android start activity, make it transparent over yours
body: <p>Basically I want to do the <a href="https://stackoverflow.com/questions/2176922/how-to-create-transparent-activity-in-android">opposite of this</a>: run another activity (that I didn't write) over top of my own, and make that activity transparent. So it would be like running another app (whatever it might be), but with a custom background.</p>