When I am not with my kids I  make sure to keep my phone with me at all times in case they need me. It may be rude to have your cell phone sitting with you at someone else dinner table and it is probably twice as rude if you excuse yourself to answer the phone. But sometimes you just have to take the call. After I took not one, but two phone calls during dinner I felt extremely rude but when your babysitter has questions you answer... right?