If you're scared about showing your unpatented invention to anyone, then you should know that there's a provision in patent law that allows you to disclose your invention for experimental use without it violating the novelty prong of patentability.
In City of Elizabeth v. American Nicholson Pavement Co. an inventor discovered a new way to pave roads using wooden blocks as the pavement. The inventor had no other way to test the feasibility of his invention but to actually install it on a piece of highway for six years to test its durability and effectiveness. He filed for the patent after his testing was complete at the end of those six years. He then filed suit when the NJ state government started using his invention without his approval.
Although this might seem like an open and shut case in which the inventor did the wrong thing, the law found that since he had no other way of testing his invention—these kinds of public disclosures are exempted from violating the novelty requirement of patentability—they sided with him. This is the Experimental Use exception.
So, if you've made a new invention but have no other way to test it out except to disclose it to the public at large, it could be covered under this Experimental Use exception. However, in light of our new patent system in which “first to disclose” includes simply explaining your invention in social media, it seems like this Experimental Use exception becomes moot. In this new system of ours, even disclosing your invention to the public at large will give you a favored patent application.
But always be sure to consult with your attorney when determining how to protect your ideas and patent chances when testing inventions.
Not sure if you should even patent your idea? Download the free whitepaper, "To Patent or Not to Patent."