It seems so far the big key to it is the software has to be installed on YOUR phone. Dont let anyone use it and if you think its been tampered with take it to your service provider and have it errased and re loaded.
Yes, that would help keep the cell phone boogy man away, OR you can always do what I do:
DON'T CARRY A CELL PHONE AT ALL! 
Of course, if you do that, everyone around you, including your spouse (like mine), will consider you a stone-aged dinosaur etc.... Life is too short, why does everyone (but me) feel it is so important to stay in such constant touch with one another?
I dont have a secretary to take my calls when Im in the shop or out on a job. I cannot afford to miss a call these days YMMV
I guess I am blessed with a 40hr/wk 8-5 job that doesn't require my attention on a 24/7 schedule.

On the other hand, there seems to be a lot of days when I wish I were self-employed.

I never really thought of Shala as being my secretary, but I guess, in a way, she is. On the rare occasions that I actually do use her cell, I have her dial it because my fat fingers are too clumsy to fit the itty bitty keyboard, and I have her hang it up too. I'd sure be lost without her. She's somewhat underpaid when I look at it like that. (don't tell her I said so)

YMMV? (My Mileage May Vary)?