My 10 yo son doesn't have a mobile phone and hes not getting one until high school, and even then it will be my old one (cruel mother that I am)
. However I don't think others in his class have phones as the school doesn't let them have them, so he hasn't really pestered me for one that much.
Meanwhile join the cruel mothers club!!
What is the schools policy with mobile phones? maybe you should raise this issue with the school and get other parents who feel the same on your side to get the school to ban them or something.
I fully agree with the other posters about phones not until high school.
Its so difficult I know as they are very good at that age at putting so much pressure on you as they feel so under pressure themselves. I gave into the nintendo ds, and a WII (although I think we must have been the last family to get one of these amongst friends and parents I know - true!!) but his current craving is for a laptop - I have stood my ground and hes not getting his way on this one! Hes got something electronic that he makes use of and has to show he can look after it. I will use this to prove to him whether his is old enough to have anything else expensive!
The other thing to try is to get him to save up for what he wants, eg pocket money, birthday money etc, so he has to then understand the value of it And if he loses it, thats it, don't give in and replace it. Cruel mother at large again 
I was shocked recently to find that some of ds's peers already have ipods and a couple have ipads. Some have everything going! Their bedrooms are full of xboxes, tellies you name it. Fortunately some of his best friends don't have lots of stuff which helps.
Kids will always pressure you for something - it was the same when we were young, just different things. I remember moaning to my parents that they were totally unreasonable to not have a telly!!! And everyone else DID have one!!