The idea that a hand-held GPS can cause interference with the airplane or it's instruments is absurd.
Please, Please, Please... take the trouble to search and read previous posts on this and other threads before posting: Doing so will prevent embarrassment to yourself such as that caused by the above quote. There are people posting on this forum who know what they are talking about, and have the credentials to prove it - Ignoring what they have taken the time and trouble to post simply wastes everybody's time and our server space.