Select a Call on Your Cell Phone

I think it would be super nice to be able to go through my phone book on my cell and select certain individuals to always have ring through or always go straight to voicemail.  For example if your wife were pregnant it would be nice, no matter what quite meeting you were in, to have her ring through in case of emergency while everyone else who tried to call wouldn't even get a vibrate.  Or while on vacation everyone from work couldn't get through while the kid who is watching your dog and garden at home would always ring through.