I have a 05 silverado with the bose stereo system and I have been trying to figure out what this input is for in the below picture... I couldn't find anything in my manual about it and was wondering if it could be a aux input maybe??

 

Just start putting things in it and see what happens LOL. I don't think that's factory(although I could be wrong). It looks like an auxillary input though like you said.

 

just follow the wires. looks like something for an aftermarket alarm. most aux inputs are a little closer to the radio.

 

I dont think thats factory, but just follow the wires, should give you an idea.

 

I agree with them.
Maybe the previous owner wanted to wear headphones? I can't think of anything that would use a plug like that. usually rca or serial type of connections.

 

it could be something for a iPod on put. My guess.

 

Id have to agree with you on that, but definently not factory

 

I have seen a truck with an after market alarm that requires a plug device to be installed into that to allow the truck to be started...aka kill switch

 

I think he'd notice that, unless the alarm has been permanently dissabled