Blocks all calls not going through Google Voice? Not sure if this is the correct place to ask, but is there a way to prevent anyone from calling my Android phone directly, so they all incoming (and perhaps outgoing, but incoming is most important) calls must be filtered through Google Voice?
I suppose one way to do this would be with a general call blocking app. I use Mr. Number Call Block on my phone, and you could set it up with the following rules:


Block all calls
Add your GV number as an exception to the blocking rule


That should allow you to basically block all calls that don't originate from you GV number. The downside to this would be that blocked calls wouldn't get forwarded through GV's call service, but rather would get sent to voicemail (or you could choose to have it automatically answer->hang up to block the calls completely).

For outgoing calls you should just be able to use the settings in the GV app. My EVO has an option do use GV for all outgoing calls, though I'm not sure if other phones do, to be honest.