Do you think it is necessary for a pri school kid to own a handphone?

I do give my 11 year old a phone. He comes home by himself by bus and train. Feel that it is necessary so as to remain contactable at all times. He needs to sms me upon boarding bus, and reaching home etc. upon reaching home, he will place his phone in our room. Strictly no other purposes like listening to music or playing games. We have a deal, if we find out that he had misuse, we will have to confiscate it. So far so good.