Been giving the scientific part a thought...but it would still seem highly improbable. It could be classified under failed body armor research. Subject's were genes spliced with both chameleon and weaver spider DNA. This was made in the hope of giving the host the ability to secrete spider silk from his sebum glands. The chameleon genes were supposed to give colour and hopefully camouflage. But the spliced genes located themselves in the hand. What was supposed to be spider silk came out as a strange too like substance. 

This is where the unlikely comes into hand...literary. With a leap of faith...

The goo is affected by the subject's desire and/or need. But as stated in the former post, the item in question must have been owned, or held and observed for a certain period of time before it can be recreated. This would also limit his ability to simple objects at first. No animate(includes plant life) or complex mechanisms(key cards are not an option. 

Is the leap of faith too big?