first - pop up activities are awesome - thanks.
they would be even better if I could create several popup activities that are hidden on the main screen.
Then add the ability to activate a popup activity from within another activity (preferably a nonhidden pop up)
This would be a huge benefit if, for example you have 8 zones of audio. You create a main popup that has 8 buttons, one for each zone. Each button opens a custom popup for that zone. I think this method would be cleaner than having to change rooms.
+1 I can think of uses for this as well… Lighting control, advanced audio video control. Activating a URL activity would also be nice… Or just add URL to buttons 
+100 Yes. I was very excited to see the popup addition, but really there needs to be some way (button, etc) to trigger a popup activity within another.
I’d like to take my custom lighting integration/controls page (which is now a popup activity) and offer it as a button on all the Theater activities to get rid of rarely used button clutter and repetition.
Then life will be complete… Almost 
+1000 YES!! Popup activities are nice, but I’d love to be able to launch from another activity remote. My projector has the ability to convert 2D content to 3D automatically, and it has lens memory to auto-switch from 16:9 to 2.35:1 format so that movies fill the entire 120 inches of my cinemascope screen. Sometimes it’s necessary to bring up the projector remote while in an activity, such as Watch Apple TV or Blu-ray, in order to quickly/manually edit 3D, picture, or format settings. It would be awesome to launch a scaled back projector remote with just those couple of buttons on it directly from the main activity remote that I’m using without having to go back to the main room and then launch it. I mostly use my iPhone with Roomie, since it’s always on me and I’m too lazy to go get one of the iPads if it’s not in the room with me already. On iPhone, I might as well just go back to the main room and bring up the projector device remote, since I can’t just quick launch the few quick buttons / directional pad that I need directly from my main activity. Please add this feature Roomie!