I use a tag "call" for any calls I need to make, and I prioritize them accordingly. I then use those priorities to determine which lists they reveal themselves in, so I'm not bothered by unimportant calls at work, etc. My Main smart lists are @Home, @Work, and @Car. I only want really important calls to show up in the list, at home I let the medium calls poke through, and in the car (where I have nothing else to to), all calls show up. Just insert the code:

@Work list: (tag:call AND priority:1)
@Home list: (tag:call AND (priority:1 OR priority:2))
@Car list: tag:call

Easy, but what a difference it makes keeping lists uncluttered!