Straight talk + unlocked iPhone 4S

Is this in the US? Which carrier?

Maybe. They are not a supported carrier. If the network is compatible, you probably can, but you may sacrifice some functionality. There is no support for this.

I've heard you actually can do this but you need a Nokia N71 which you can buy from straigh talk in order to activate the sim. I guess theres a pretty involved process to got it to work but it is possible.

I am in the process now of trying to port my phone number from a Boost mobile account to Straight Talk, and it has been a complete nightmare. Straight Talk customer service had denied i paid for activation, but my bank shows they took $49.15 from my account! NEITHER my boost phone nor my iphone work now!

Straight Talk now sells a micro sim card to be used with an iphone. You do not need to buy a Nokia phone for it's sim card. The Straight Talk sim card is purchased from them online for !5 bucks. hope it works for you. It hasn't yet for me, but i've only been waiting since Sunday July 15, and it's only monday the 16th. They did say it could take up to two business days, so I am TRYING to be patient while they deny they took $49 out of my bank account.

You MUST correctly create a custom APN profile. I think the one i created is not what works, so I'm trying to learn how to delete it and create the right one according to Straight Talk's instructions on their activation card for the sim.

If you look at the dates of the posts you are responding to they were made prior to Straight Talk supporting the iPhone.