I would consult a patent attorney, and get a patent search. Cost is about $600. If patent search does not show anything like your invention, then make an application for a patent. Cost about $3000. These are ballpark figures and the price can vary.
I would contact Jack Lo. He is a patent agent. He also wrote a book on patenting things. He gives a half hour consultation free. You can also email or phone him. He will fax or email you a NON-DISCLOSURE AGREEMENT. He has personally patented some ELECTRONIC items, and has assisted many people in patenting a variety of items:
Jack Lo jacklo@thepatentfirm.com
617 Viewridge Drive
Pacifica, California 94044-2162
United States
Telephone: 650-355-6666
Fax: 650-355-5550
He is a very nice and approachable man. I have not met him in person yet. I have an electrical/electronic invention that I need to pursue also. I have made basic email contact with Jack and he was very helpful. He is not a shyster. He is also somehow connected with the electrical engineering department at the University of Washington in Seattle. You can ask him about that if you want. I noticed that several of his patents were a collaboration with UoW engineers.
PS: Another route to go is: Nolo Press has a computer program called PatentPro Plus (link) that will walk you through the whole patent process on your own. I think it's about a $300 MSRP program.
Here is another contact which I know nothing about: anon-ipattorney@craigslist.org
He might be able to direct you in the right direction.
Also, you can do your own basic patent search online. You need to download a special viewer to "see" the patent drawings.
Here's the patent search link: Patent Office search
Tip: Use as few search words as possible at first, then add words to expand your search, or subtract words to narrow your search. You can also use Boolean techniques for searching.
Here's the viewer link: Viewer details I used AlternaTIFF: AlternaTIFF
You have to use IE, Netscape, or Opera browser to use this viewer.
Close and re-launch your browser after you install the viewer.