i think Sloane didn't take the device. my bet is that Lindsey wouldn't have given up the device for Sydney's life. and i think he was testing to see if even though he didn't give it to them, that they'd deliver Sydney anyways. because the covenant never would have released Sydney if they got the box and the device wasn't inside. they would have kept her, or in Lindsey's mind, maybe killed her if she really was being held by the covenant. so then Lindsey would know that it was all staged by Jack. that's my theory.
also, i totally knew that Lindsey would eventually be dead. i didn't know when or how, but you just don't threaten Sloane. he'll just kill ya. it's not like he's got morals. and Lindsey isn't smart enough to be able to prevent Sloane from killing him. and he asked for it even. he said he wanted Sydney dead, and he threatened to expose Sloane's master plan, which i'm starting to think Lindsey might actually have had a clue about. and maybe that's one reason Sloane killed him.
also, i totally knew that Lindsey would eventually be dead. i didn't know when or how, but you just don't threaten Sloane. he'll just kill ya. it's not like he's got morals. and Lindsey isn't smart enough to be able to prevent Sloane from killing him. and he asked for it even. he said he wanted Sydney dead, and he threatened to expose Sloane's master plan, which i'm starting to think Lindsey might actually have had a clue about. and maybe that's one reason Sloane killed him.