I searched too much about opening a dialog from a service or broadcast receiver, and there is no answer, but i see opening a dialog via broadcast receiver in this app:
this app is an audio manager which you can change volumes and set profiles as soon as android volume changed (for this we should register a broadcast receiver with VOLUME_CHANGED_ACTION action) the interesting point for this app, is that it open's a dialog, not a themed activity or transparent activity, it seem that open a dialog, because this pop up don't stop current activity and treat like volume seek bar when you click volume up and down keys. all of back environment are clickable!!
here is my app that use transparent activity:
when i open my dialog, it's stop current activity(for example, stop the game, while in game called) , and in many cases, it open a bit slower than Fine Volume Control app, it's appeared fast and close fast, and finally make the back environment dark(but Fine volume control doesn't make background dark)
summary: how can I open a dialog in everywhere like this app Fine Volume Control which don't stop current activity?