I totally agree regarding the tantrums, and timeouts are pretty uneffective until the age of 2.  If you would like a slightly unconvential way to stop the touching this is what I did and it worked wonderfully. If you use your thumb and middle finger to "flick" their hand it stings a little and is unpleasant but your are not teaching them to hit or slap. Young children are not able to mimic this "flick" action. After a few times all I had to do was warn my children and the behavior stopped.

There is an AWESOME program called 'Parenting with Love & Logic' [I think Jim Fay is founder - http://www.loveandlogic.com/] that works very well. You can order materials from their website or find local classes. You might also contact your local community education program or local school district and ask to talk to a counselor who might have information availablt. 'Love & Logic' teaches you how to parent your children to make their own decisions [good or bad] and help them accept the consequences to those decisions, such as touching the phone. You would tell your son that he may not play with the phone, or if he chooses to do so, he will then be choosing to spend a few minutes in time out or without his most favorite item. The key with any discipline is CONSISTENCY. If you are not consistent, then the issue becomes worse. Good luck!