Hi FLSR,
1. We're making improvements to leaving the voice control on in the background, but what you suggest really isn't possible to do with the iOS 7. It might be possible to tie voice control to a geo-fence, but I can't make any commitments here due to the specificity of that feature. IE, quite a bit of work and not clear that everyone would see the benefit.
2. Currently Voice Control does not support setting specific dim levels: http://mobilinc.com/features/voice/
This is on our investigate list and do if it doesn't impact reliability.
Wes