Dual Sim Phones

good timing on your thread. just y'day my buddy was showing me something he picked up from amazon.com for his iphone.

so apparently he's got this back hard case thing, that's connected to the iphone 4S (not i5) that lets him use a secondary sim card. so he's running dual sims on his 4s. i called his 1st number and his usual ring tone was heard. i called his second number and it rang with a different tone. Also, i noticed that when the phone was unlocked, his 1st number (default sim in the iphone) had the usual red answer call button. his 2nd number (secondary sim attached the external case) had a blue answer call button.

flipside - he couldn't recieve SMS's on his secondary sim. this was not mentioned in the ad on amazon and/or the box.

I would like a dual sim phone, but I don't expect Apple to do it. It doesn't seem like there have been many phones that have had that option.
I know I am in the minority wanting a separate line for work. It does give me an excuse to carry around two iPhones.