My phone is now dead due to "Sudden Death Syndrome" - it couldn't be revived even with a JIG Cable which is rather depressing - I thought I'd share how to tell if your SIII is about to kill itself since it's the 200day mark for quite a few SIII's out there now:

Read more: http://forum.xda-developers.com/showthread.php?p=36499838

1) Your phone, it's randomly freezing bro:

You're happily playing "The Impossible Game" when you're almost through the level and your phone suddenly freezes, you can't turn it off, you can't reboot it, the only course of action is to rip out the battery and lose your hard work (that's what has happened to me ugh)

2) After freezing, you think this might be an application causing it?

That's what I thought too with my phone, so I did a factory reset only to find that it was freezing within 10mins even with no apps installed, I knew there was something up.

3) Must be my ROM then?

Ah, so you're like me who was running a custom ROM at the time? I thought it was the ROM too, so I updated it, restored it, did a head twirl and still, nothing, it kept freezing, I was scratching my head, I was distressed, my whole... life... is on this wee device of mine in otherwords... Crap.

Things I've tried:
Restoring to stock.
Installing Cyanogenmod 10.1, Android Revolution HD
Custom Kernels "with the magical fix embedded" - Perseus, Siyah
Different Flashing Tactics, Mobile ODIN, ODIN, Heimdell, CWM

All tested over the course of a week

So this sounds like me, what the hell do I do?
Send it for repair, it's the only way bro, don't waste your time. Crashes can happen randomly, if you're running some kind of custom rom or are rooted and notice your phone freezing restore to stock - else you'll wake up one morning and your phone just won't turn on or do anything.

Samsung claim to cover you under warranty since this is a manufactures defect even if you're on some other ROM but if you get the chance just restore to stock to prevent our local repair companies from trying to take all of your hard earned cash unless if you argue.

Oh, and if you're on a custom ROM you'll need this before restoring to stock: http://forum.xda-developers.com/showthread.php?t=1494114


----

Update: I got my phone back from "repair" with the software just reflashed, as soon as I read the ticket I should have just demanded them to take it back except I was in a bit of a rush, Samsung reflashed my phone with the latest software and called it fixed. Since this is a hardware fault they're either needing to replace your mainboard or in extreme situations replace the whole phone. When sending the phone back for repair if they've done this to you include a screenshot of the "eMMC Brickbug Check" app running on your phone (if possible) along with the note "See image, please replace mainboard, sudden death syndrome"

I've noticed that Telegistics know what they're repairing and never seen a phone come back without having the mainboard replaced (kudos to them!), since my phone was bought online from 2Degrees they've made me deal with Samsung direct.

In the meantime, the ultimate fix was buying the Nexus for me.