Hmmm...
I'm 14. Do I still count as a kid/child? I consider myself mature enough to make a point, so here goes:
General rules: bells and whistles need to be shot. Camera phones look like shit. Unless it's also a protective device, you don't need a skin on whatever gadget you've got. Yes, text messaging can be convenient in some cases, but if you are texting someone a message that would be much more suitable to audio contact, you suck. It's taking you far longer and costing you extra money in some way. If it's during class, PUT IT THE FUCK AWAY AND LISTEN TO THE GOD DAMN TEACHER. Socialize during passing period, that's what it's there for. And for the love of God, don't ***** if your phone gets taken away. They have rules about that crap for a reason.
Cell phones: no kid needs one of these until mid-to-end middle school or beginning high school. Certainly not a elementary-level student, and certainly not a five-year-old. What the hell is a five-year-old going to do with a cell but play with it? Or make calls to weird long-distance numbers or something.
MP3 players: roughly the same guidelines as above. If you can find a phone/MP3 combo device (most things are, nowadays) then that should do fine. If they're younger than the suggested ages above, a simple disc player or something should suffice, but seriously: where the hell is your child going that they need portable music and you're not going to be with them?
Laptops: you don't need a laptop until college, unless you're going to study abroad for extended periods or something like that. Again though, most people studying abroad are in college. Some HS students do spend summers in other countries though so maybe.